The 2025 hurricane season has been quiet so far with four extremely short-lived storms. A quiet (or active) start to any season always brings the question, will the rest of the season continue this way? One way to try and answer this is by looking at patterns of ocean temperature around the world. While El Niño-Southern Oscillation (ENSO) conditions in the Pacific often draw significant attention, there is a similar phenomenon in the Atlantic, referred to as Atlantic Niño/Niña, that also impacts hurricane risk. Notably, the Atlantic Niño/Niña region has experienced significant cooling over recent months, now aligning with La Niña conditions. This cooling may reduce hurricane risk by limiting the formation of hurricane seed storms off the African coast.
The possibility of this pattern was indicated as early as January, when forecasts suggested that Atlantic La Niña conditions could emerge during the hurricane season, albeit there was considerable uncertainty. It remains uncertain whether these Atlantic La Niña conditions will persist throughout the season or significantly influence it given the multitude of variables that impact hurricanes including the Madden-Julian Oscillation, steering flows, and Main Development Region temperatures. Nonetheless, it will be an interesting substory as the hurricane season progresses toward its peak.
In wildfires, buildings are only as resilient as their most vulnerable features. It’s often assumed that homes with metal roofs will perform better during fires than those with asphalt shingles, which are more flammable. However, analysis using the Cal Fire Damage Inspection database — which tracks all structures damaged by wildfires in California since 2012 — reveals little difference in performance between single-family homes with metal and asphalt roofs. One reason is that homes with metal roofs are more likely to have wooden walls, while those with asphalt roofs are more often built with more-fire-resistant materials. This simple example highlights the importance of considering a building’s complete set of features when assessing its wildfire resilience. Focusing on just one or two attributes can provide a misleading picture.
Caption: Assessment of the influence of roof type and wall type of wildfire vulnerability. Left plot shows average damage of buildings in wildfires with 50+ buildings with asphalt and metal roofs in the Cal Fire Damage Inspection Database (https://data.ca.gov/dataset/cal-fire-damage-inspection-dins-data). Average calculated assuming categories ‘No Damage’, ‘1-10% Affected Damage’, ’10-25% Minor Damage’, ’25-50% Major Damage’, ’50-100% Destroyed’ which are given values of 0, 5, 17.5, 37.5 and 100% loss, respectively. Right plot shows proportions of different wall siding types for locations used in the lefthand plot.
June 1st is right around the corner, and with it the start of the Atlantic hurricane season. When we issued our seasonal outlook in March, we forecast slightly above average activity for the upcoming season. Since then, ocean temperatures in the Atlantic have continued to cool from their 2023 and 2024 peak (1st image). This is good news for 2025 hurricane risk as cooler ocean temperatures mean less fuel for hurricanes.
We can translate what the recent cooling in the Atlantic means for hurricane risk using Inigo’s in-house model. Our model updates each month and forecasts ACE west of 60° longitude (ACE 60W). ACE 60W is a measure of total hurricane activity in the western part of the Atlantic Ocean, and our work has found this metric is connected to economic and insured hurricane losses in the US. Our model was forecasting an above average season for much of the early part of 2025, but has backed off those predictions in the latest May update (2nd image). No prediction is perfect, but hopefully 2025 is quieter than the 2024 hurricane season.
As winter turns to spring, flowers begin to bloom and seasonal hurricane forecasts are about to be released. There will be a lot of seasonal hurricane predictions coming out in the next few months and almost all of them will rely on the six-month sea surface temperature (SST) forecasts released by national modelling centres. This raises the question, how accurate are these six-month SST forecasts?
There’s a lot of different ways that we can evaluate how good or bad a forecast is, but one straightforward way is to look at how well it has performed in the past. The plot shows SST forecasts for the Main Development Region of the Atlantic Ocean over the past 18 months, released by ECMWF, a leading modelling centre. By comparing past forecast anomalies (grey lines), released monthly, to observed SST anomalies (yellow line), we can see that the forecasts have correctly predicted the cooling trend in the Main Development Region since June 2024. However, they have often been too aggressive with the cooling (grey forecasts are mostly below the yellow observations). Looking ahead to the start of hurricane season in June, the forecasts predict continued cooling, which would significantly lower hurricane risk compared to 2024. Whether the latest forecasts (blue line) are accurate remains one of the major questions that organizations releasing seasonal hurricane forecasts will need to grapple with. Inigo will be releasing our view in the coming weeks, so stay tuned!
AI technology is now ubiquitous, with specialised hardware and software playing crucial roles in the development and deployment of artificial intelligence models. Popular frameworks like TensorFlow and PyTorch run seamlessly on multiple types of hardware and Graphics Processing Units (GPUs) and Tensor Processing Units (TPUs) are extensively employed to solve computational fluid dynamics problems.
In a recent paper co-authored by Boyang Chen, Amin Nadimy, and colleagues, we demonstrate how convolutional layers commonly used in neural networks can help solve complex partial differential equations. The paper, titled “Solving the Discretised Shallow Water Equations Using Neural Networks“, showcases this innovative approach. The NN4PDEs framework, developed by the Applied Modelling and Computational Group at Imperial College London, enables these use cases. In this method, the convolutional layer provides a discretisation scheme to solve the equations. Though conceptually simple, the paper illustrates the practical implementation for complex equations like the shallow water equations.
Importantly, these tools can effectively model flood risk with the accuracy and spatial resolution needed to represent local water depth during significant floods. We applied this to simulate the flood event impacting Carlisle, UK, in January 2005. The figure below, from the paper, depicts the problem setup and the solution provided by this approach.
While this early work demonstrates that the NN4PDEs approach achieves results and computational performances comparable to traditional computational fluid dynamics tools, it also paves the way for further applications. These applications can seamlessly combine AI models and physics on different scales or allow scaling up hardware to solve complex fluid dynamics problems over large domains.
Wildfire Whiplash – sudden shifts with painful consequences.
Rapid transitions between wet and dry conditions can increase frequency and severity of natural catastrophes like flash flooding or wildfires. The unprecedented wildfires that have devastated Los Angeles County are, in part, a result of this phenomenon. The figure below shows cumulative precipitation data recorded by a rain gauge in downtown LA since 1907. After two exceptionally wet seasons in 2022/23 and 2023/24 (blue lines), the LA hills experienced an explosion of grass and brush growth. However, since then Los Angeles has endured its second driest June to January on record (red line), desiccating the landscape and creating a highly flammable tinderbox environment. The combination of this abundant fuel, alongside strong winds and ignitions has led to the most destructive wildfire season ever recorded.
Inigo has established a partnership with climate scientist Daniel Swain (UC ANR & UCLA) to better understand US wildfire seasonality and associated risks. His latest publication on ‘hydroclimactic whiplash’ is extremely timely and an excellent summary of it can be found on his website – Hydroclimate volatility on a warming Earth – Weather West.
Santa Ana winds intensified the ongoing Franklin fire in Malibu, California, forcing mass evacuations and valiant firefighting efforts. These hot, dry, powerful winds desiccate vegetation, carry embers, and increase flame length, accelerating wildfire spread. From 1990 to 2009, 50% of burned area and 80% of wildfire economic loss in Southern California was linked to Santa Ana winds (Kolden et al., 2018). More recent examples include the 2017 Thomas and 2020 El Dorado fires, which together burned over 300,000 acres.
Climate change is increasing annual average air temperatures and wildfire burned area across the Western US (NOAA, NIFC), but its impact and Santa Ana winds is uncertain. These winds are generated by pressure gradients between the warm Great Plains and the cooler Pacific Ocean that typically form during the autumn months. Reanalysis of weather data from 1979-2020 reveals that strengthening temperature gradients between coastal California and the continental interior may be increasing the frequency of these events (Thompson et al., 2023). However, global climate model outputs suggest that the frequency of Santa Ana winds may decline over the 21st century as the annual window of favourable conditions narrows (Guzman-Morales and Gershunov, 2020).
Though the evolution of Santa Ana winds as the climate changes is unclear, their devastating effect on wildfire activity continues to increase. California’s rainy season arrives ~27 days later than it did in 1960 (Lukovic et al., 2021). A extended wait for wildfire-relieving rains prolongs the period where vegetation dried over the summer months is exposed to Santa Ana winds. As a result, we may see an increasing number of late-season Santa-Ana-fuelled fires like the Franklin fire in the future.
Solid and dashed blue lines show the mean monthly precipitation for California between 1943-1963 and 2010-2023, respectively (National Oceanographic and Atmospheric Association). Yellow bars show the monthly average number of Santa Ana events recorded between 1948 and 2012 (Guzman-Morales et al., 2016).
Earlier this year on September 27th Asheville, NC was the center of the devastation brought by hurricane Helene, with record-breaking rainfall which resulted in extreme flooding. The flooding inundated homes, businesses, and roads, displacing hundreds of residents and leading to billions of dollars in damages and hundreds of houses destroyed in Buncombe County. With 227 fatalities Helene became the deadliest hurricane to hit the US since Katrina in 2005.
With one of the longest daily rainfall records in the U.S., dating back to the 1870s, Asheville’s historical data highlights the peculiar nature of this event. The figure shows, for each year in the historical record, the maximum 24-hour (blue) and 72-hours (yellow) rainfall totals. While Helene’s 1-day rainfall (and peak rainfall rate) were significant but not unprecedented and were exceeded at least twice in the historical record, the 3-day total far exceeded anything in Asheville’s history. This record-breaking 3-day rainfall was fuelled by two days of heavy rain before Helene’s arrival, caused by a unique meteorological setup. The precursor rain saturated the ground and raised river levels, leaving the region vulnerable to catastrophic flooding once Helene made landfall.
This event highlights the growing challenge of preparing for extreme weather. The sequence and intensity of rainfall, rather than daily peaks alone, proved decisive in causing the devastation. At Inigo, we’re prioritizing the evaluation of flood risk models and maximizing our learning from these events to improve our preparedness and resilience in the face of increasingly severe weather patterns. Asheville’s experience underscores the urgency of better understanding flood risk and adapting to a changing climate to mitigate future risks.
AI weather forecasting is in the news again this week, with Google DeepMind’s release of GenCast. AI weather models have made rapid progress for forecasts up to 15 days in advance, but less progress has been made on the notoriously difficult problem of seasonal predictions. Accurate seasonal predictions would provide an opportunity for society to prepare well in advance of hazardous conditions. Here at Inigo we’ve spent the last few months refining our strategy for seasonal hurricane prediction. A major part of that work has been creating I-SPARK (Inigo Seasonal Prediction and Analysis of RisK), a new AI tool to help make accurate seasonal hurricane predictions at insurance relevant lead times of three to nine months.
I-SPARK uses freely available sea surface temperature forecasts to predict the level of risk for the upcoming hurricane season. The figure shows some of the sea surface temperature regions that the model will be using to make its December initiated forecast in a few weeks time. Interestingly, our model disregards most ENSO information until after spring due to low predictability. As the figure inset shows, the model skill rapidly increases by February, but then falls off in spring. This gives us confidence that useful hurricane risk information can be derived as early as February, but we need to do more work to understand why the model struggles in spring.
This work is being presented at the American Geophysical Union conference in early December, 2024. You can check out the full conference poster and additional details on GitHub. Please reach out if you want to learn more.
The 2024 hurricane season began with the earliest Category 5 hurricane ever recorded. In an unprecedented twist there was an eerily long and unexpected lull during the peak season, before ending with a flurry of activity in the Gulf. Next month, Charles Powell, from the University of Cambridge, and I will be sharing a retrospective of 2024 as part of the work that Inigo is funding under its InSPIRe programme.
The chart compares the timing of the first and last major hurricanes for the climatological periods 1980-2020, 1980–2000 and 2000–2020 and compares these to 2024. The vertical lines denote the temperature range between the first and last major hurricane and the horizontal line the mean temperature. From the climatological data we can see that there is a fairly well-defined start to the first major hurricane in the season, but that the end of the season appears to be extending, with the last major hurricane occurring later in the 2000–2020 period compared with the earlier 1980–2000 period. The first major hurricane of 2024, Beryl, is a remarkable outlier becoming a major hurricane on the 30th of June. The last major hurricane of 2024, Rafael, reached major hurricane status on the 6th of November, which, while not unprecedented, is approximately two standard deviations from the long-term mean.
Our analysis shows that the average temperatures in the Atlantic main development region have increased between the early and later periods, 1980–2000 and 2000–2020, with 2024 being one of the hottest years on record. As global temperatures continue to rise due to climate change, warmer oceans are able to sustain major hurricanes earlier and later in the season potentially leading to extended hurricane seasons This could pose a challenge for the insurance sector, as amplified hurricane risk over a longer season increases the potential for catastrophic loss events.
Typhoon Shanshan made landfall in the Kagoshima Prefecture of southern Japan on August 29th bringing considerable flooding and rainfall with it. Some areas broke rainfall records with over 300mm of rain in 24 hours. Early forecasts showed the potential for even more catastrophic outcomes with the storm forecast to make landfall as a powerful typhoon between Osaka and Tokyo, a highly populated area. However, the storm ended up making a sharp turn westward before turning north and making landfall (yellow track on map). The map below shows the forecast tracks for the ECMWF traditional and AI models initialized on August 23rd with the forecast strength of the storm indicated by text in each track point.
Weather models generally did a poor job forecasting this storm. One of the first models to pick up on the westward turn was the AI model run by ECMWF (blue track), one of the world leaders in weather prediction. In many ways this was a win for the AI models, they accurately forecast the track of a dangerous storm hours and days before traditional weather models (the ECMWF traditional model is the orange track). However, this success came with a massive caveat. The ECMWF AI model forecast the westward turn, but also forecast the storm would never rise above tropical storm strength, a known and recurring issue for AI weather models. In reality, the storm briefly reached category 4 strength, with sustained winds of 215km/h, before weakening to a category 1 storm prior to landfall. All together, Typhoon Shanshan presented an interesting case study in the promise and shortcomings of AI weather models.
Inigo Welcomes Patrick Ball to the Climate Science Team.
“As a Risk Scientist within Inigo’s Catastrophe Research team, my role is to help our underwriters and exposure managers leverage the latest scientific advances and cutting-edge technology when assessing the likelihood and impact of natural disasters to our insurance portfolio. This work includes evaluating and optimising catastrophe models, collaborating with academic institutions and insurtech companies, and performing bespoke research projects. This scientific data-driven approach ensures Inigo stands out from the crowd! While our team covers all natural disasters, my specialty is earthquakes. I hold a masters and PhD in Geophysics from the Universities of Oxford and Cambridge, respectively, and prior to joining Inigo I worked as a researcher at several universities and a catastrophe model vendor”.
Idalia made landfall as a major hurricane this week in a season where we’ve been anticipating what might become of a Battle Royale between the anomalously warm seas in the Atlantic and an ongoing El Niño in the Pacific. A reminder: we’re not even climatologically half way through the season yet…
Taking a look at the sea surface temperatures in the Gulf of Mexico, it’s little surprise we saw a strong landfall: in the week leading up to Idalia, the sea in its path was the warmest it’s been in since 1982 (when this particular sea temperature dataset started). The chart here shows the average sea temperature for the period of Aug 23-29th for every year for the past 40 years in the red box shown that broadly straddles the region through which Idalia passed and developed. Naturally other factors will always influence how a storm develops, but you don’t typically get the heavy-hitters of hurricanes without the warmer seas.
And now for the rest of the season…
Lahaina, located on the northwest coast of the Hawaiian island of Maui, experienced a devasting wildfire in August 2023. Several factors likely contributed to the severity of this wildfire including enhancement of strong easterly winds by Hurricane Dora, Katabatic winds flowing from the West Maui Mountains, located to the east of Lahaina, and drought conditions.
The precipitation rate for all of Hawaii has been extracted from the NCEP Reanalysis data between 1980 and 2023 and is shown in the graph. The precipitation rate for February 2023 was the highest recorded since 1980 at nearly three times the average. Precipitation rates throughout the spring were above average but by June it is below average, with July being extremely dry in the bottom 5% of years.
The February and spring rainfall likely contributed to a growth of vegetation. During dry seasons an increase in fuel availability contributes to the wildfire risk. Precipitation rates over Hawaii have been well below normal for June and July leading to drought conditions across Hawaii. According to the US Drought Monitor the most severe droughts over Hawaii in South and West Maui (where Lahaina is located). It is likely that the drought conditions combined with an abundance of fuel from the wet February and spring were contributory factors in the severity of the Lahaina wildfire.
The Copernicus Climate Change Service produces monthly seasonal forecasts from many different weather forecasting centres to help us understand possible future conditions around the globe.
The chart below shows the expected rainfall through the months of September to November from five different seasonal forecast models. Greens show rainier conditions, brown shows drier conditions. The rainier conditions can be indicative of increased tropical cyclone activity. This year we have an El Nino – that usually weakens hurricane activity – but a warm Atlantic, that can increase activity. So, any indications of what is come in such a difficult year to forecast are always useful.
It’s interesting to note the green, wetter region across the Tropical Atlantic. However,this region exists more towards the central / eastern Atlantic, which may be indicative of a busier hurricane season here, but this anomalous wetness is reduced towards the eastern seaboard of the US – although rainfall is still expected to be slightly above average here. All to play for with the three key months ahead – but will we be spared hurricane landfalls with a busy tropical season staying over the sea?
While by many definitions the traditional “fire season” does not begin until spring, it would be a major omission to not at least briefly discuss the catastrophic wildland-urban interface firestorm that unfolded in the Los Angeles region in January 2025. Even now, in September, thousands of Californians are still grappling with mass displacement and insurers are still managing what have been in some cases record-breaking losses. And that this event occurred at a seemingly unusual time of year highlights a subtle but important reality: in some locations, major wildfire activity can occur well outside the warmest months of the year.
Though winter fires may be less common in most settings, they can still be highly consequential if they do occur (especially as preparedness may be lower this time of year due to the perceived lower risk level). This is exemplified by the December 2021 Marshall Fire–a primarily grass and brush fire on the high plains just east of the Rocky Mountain Front Range that destroyed over 1,000 structures in the suburbs between Denver and Boulder, Colorado amid an extreme wind event following record-breaking antecedent warmth and dryness.
Such winter fires, while still relatively uncommon, are perhaps less so than previously believed–and may be occurring more often as the climate warms and as strong winter wind events become increasingly likely to coincide with dry vegetation conditions. Recent experience, therefore, suggests a growing need for an expanded definition of what constitutes “fire season” in western North American (and perhaps also elsewhere).
While these devastating events in early 2025 may have set the tone for the more traditional fire season months that followed, subsequent wildfire-related losses in the United States as of early September have been, thankfully, relatively modest. Despite a rather active fire season overall, a large majority of the largest and fastest moving fires with greatest destructive potential have occurred in remote areas away from population centers. As is further discussed below, however, fire season is not over yet and there is reason to believe that some regions in the Western U.S. may yet face the potential for additional destructive fires in 2025 before all is said and done.
The North American Monsoon–a seasonal reversal of the prevailing (dry) westerly winds to (moister) easterly winds–typically brings much-needed seasonal rains in the form of afternoon and evening thunderstorms to much of the Desert Southwest, Great Basin, and southern Rocky mountain states beginning in August and continuing through August or sometimes September. Accordingly, the hottest temperatures of the year often occur in the Southwest U.S. deserts in May or June–before cooling clouds and downpours arrive. This year, however, the monsoon was largely a “no-show” in July and even into mid-August–allowing peak summer temperatures to persist into August and setting new extreme heat records in cities like Phoenix. One notable exception to the elevated heat this summer was the Pacific Coast of California–which, due to stronger-than-expected oceanic upwelling of cold ocean waters, remained substantially cooler than the long-term average (despite unusually warm conditions across California’s mountains and deserts).
This combination of widespread near-record heat and a delayed monsoon onset allowed fire season in Arizona, Utah, Nevada, and western Colorado to continue at an elevated level of intensity for much longer than is typical–and numerous large fires burned across the region for nearly the entire summer. Perhaps the most notable and largest of these fires was the Dragon Bravo Fire, which occurred along the North Rim of Grand Canyon National Park. The fire, which was ignited by a lightning strike amid historic vegetation dryness, ultimately went on to burn nearly 60,000 hectares (~146,000 acres, becoming the seventh largest in Arizona history) and over 100 structures–including the historic Grand Canyon Lodge and most of the North Rim park infrastructure (and also led to a toxic chlorine gas leak from a burned water treatment plan, requiring evacuation of firefighters and visitors alike). Meanwhile, in western Colorado, the Lee Fire went on to become the fifth largest in state history after burning around 56,000 hectares (~138,00 acres), though it only destroyed a handful of structures due to its relatively remote location.
During July and August, multiple strong “pyrovortices”–essentially wildfire-generated tornadoes akin to their severe thunderstorm-derived counterparts and similar in strength–occurred on various interior Western North American fires. These types of events, which are distinct from lesser “fire whirls” that occur on fires of all sizes and intensities, form when the extreme but localized heating generated by an intense fire combines with ambient wind shear to cause the ascending column of air atop the fire to rotate rapidly, and sometimes violently. Remarkable footage of these well-documented events highlights the risk such phenomena pose to firefighters and even to nearby structures. Fortunately, during the North American fire season of 2025, there were no serious injuries associated with these vortices due to a combination of luck and increased firefighter awareness.
Research into wildfire-generated pyrovortices is in its relative infancy, though there has been an anecdotal increase in the documented occurrence of such events in recent years. Some of this increase likely stems from the increased ease of documentation of this relatively rare phenomenon in the smartphone video recording era. But recent experience with intensifying wildfires in multiple regions globally (including the western United States and western Canada, southern Europe, and south-eastern Australia) suggests that various “pyroconvection”-related hazards–i.e., those related to fire-generated thunderstorm or thunderstorm-like clouds reaching well over 10km in height, including tornado-strength vortices–may be a growing hazard as wildfire burn environments become more volatile. Indeed, among researchers globally, there has been growing convergence between the fire weather and severe convective weather communities amid increased recognition that many of the most extreme wildfire events share striking similarities with, and can even cause, severe thunderstorms.
As of this writing in early September, a substantial escalation in wildfire activity from central California well northward into British Columbia and even the Northwestern Territories of Canada was underway. This late-season wildfire outbreak was facilitated by a number of factors–most prominently including a major heatwave (which set new all-time September monthly temperature records at its peak in western Canada) and hundreds of new fire ignitions from recurrent waves of thunderstorms. Some of these thunderstorms were “dry,” meaning they generated lightning but little to no co-occurring rainfall (something that recent research suggests may be a growing challenge in a warming Western U.S.). In some cases, strong and erratic outflow and downburst winds from thunderstorms pushed lightning-ignited fires in unexpected directions. Amid such conditions, much of the small and historic community of Chinese Camp in the Sierra Nevada foothills of California was destroyed by fast-advancing flames on September 2nd.
Remarkably, over 142,000 lightning strikes occurred in California alone between August 1 and September 4. Fortuitously, however, most of these struck in regions not presently affected by drought in northern portions of the state–limiting both the total number of lightning fire ignitions and the intensity of subsequent fires compared to what would most likely have transpired under severe drought conditions (as occurred during the 2020 August lightning “fire siege”).
The effect of this recent heat and lighting was compounded by a widespread swath of moderate to extreme drought in the Pacific Northwest states of Washington and Oregon as well as western Canada, especially British Columbia. Here, fire season typically fades by early autumn but this year remains at near-historic levels of activity as of early September, with numerous high-intensity fires burning in forested regions. Widespread and locally severe smoke pollution have resulted, triggering air quality warnings and public health alerts, with vast plumes of smoke extending eastward thousands of kilometres and across much of the North American continent. Some beneficial rain is expected across much of the region in coming days–especially across Oregon and north-western California–but likely not enough to end fire season in most locations. Should another heatwave or major dry wind event occur thereafter, fire activity will likely increase substantially once again.
Severe to extreme drought has persisted since the spring for a broad portion of the interior U.S. West, extending from southern California eastward across Arizona and Utah to western portions of Colorado, Wyoming, and New Mexico. While the onset of seasonal rains in the Pacific Northwest and northern Rocky Mountain states will likely end fire season in the coming weeks, much of the interior West as well as central and southern California will remain primed for elevated wildfire activity well into the autumn, and potentially into the early winter months–especially during periods of strong winds. Across central and southern California, strong and dry downslope winds tend to occur most often from September through January–often in alignment with very dry vegetation conditions. Across the Rocky Mountains, strong winds in autumn can also occur but cooler and moister conditions are often a limiting factor.
In autumn 2025, given pre-existing drought and seasonal predictions of pointing to greater-than-average odds of further anomalous West-wide warmth and possibly dryness in the interior, elevated late-season wildfire activity may occur across a wider than usual region (i.e., not only in coastal central/southern California but perhaps also in portions of the interior Rocky Mountain region). Additionally, elevated wildfire risk in coastal southern California may linger well into autumn or even beyond–a consideration that is top of mind for many in the region following January 2025’s devastating Los Angeles fires.
Fire Season 2025 has been an unusual one in multiple respects across the Western United States. First, it is highly likely that the most destructive fire events of the entire year (by a wide margin) will have occurred in January–a month not historically considered to be a likely contender for what may ultimately become the single costliest wildfire disaster in history. Second, wildfire activity in western North America experienced a lull from mid to late summer before roaring back by early September–with indications that above average activity might continue much later into the autumn than has historically been typical in some regions.
Also notable has been the divergence between the above-average number of wildfires this year yet below-recent-average area burned in the United States–and, contrarily, the near-average number of fires in Canada but dramatically greater than average area burned.
In the western United States, this pattern appears to be due to several opposing influences. Widespread drought and elevated lightning activity yielded a landscape receptive to ignitions and a ready source of ignitions, respectively–contributing to the elevated number of fires. Yet episodes of elevated fire activity this summer were not strongly clustered in time (allowing time for firefighting crews to move from fire to fire without substantially depleting resources), and also generally did not coincide with major large-scale windstorms (thus avoiding sustained periods of rapid fire spread). Thus, despite a historically hot and dry summer in some parts of the interior West, historic wildfire conditions were fortuitously not observed through the end of August.
In western and central Canada, however, the situation has been very different. Despite a near-average number of known ignitions, fires have burned an extremely large area, primarily in boreal forests–and as in recent severe fire seasons, there have been mass displacements from remote communities and voluminous long-range smoke transport that has affected cities as distant as New York and Washington, D.C.. In fact, were it not for the record-shattering Canadian fire season of 2023 before it, 2025 would already have set a new record for area burned in the country. The effects of a warming climate on Canadian wildfires has rapidly become more apparent in recent decades, as the influence of an increasingly “thirsty” atmosphere tends to exert the strongest influence in densely forested environments (such as those that cover much of Canada’s land area).
Ultimately, these observations about the unusual and still-unfolding fire season of 2025 emphasize a couple of broader lessons. First, neither the number of ignitions nor the area burned by wildfire tell us what we need to know about the societal and ecological impacts of those fires. Despite being relatively modest in size, the Los Angeles fires in January were the most destructive on record; although the United States has experienced an elevated number of fire ignitions so far this year, the area burned has thus far remained below the recent average (whereas in Canada the opposite has been the case). And finally: seasonal predictions can only tell us about the fires to come. Antecedent conditions and long-term climate trends are indeed quite important, but the number, location, and timing of ignitions as well as the occurrence of strong wind events are also critical–yet only the former are potentially predictable at seasonal scale. 2025 has already brought some surprises, and there may yet be a couple more in store before the season is over.
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