Rising Temperatures Push Wildfire Risk Into New Geographies, Reshaping Insurance Exposure

Spokane Burns While a Global Pattern Intensifies

Wildfires that erupted around Spokane, Washington, over the weekend have destroyed hundreds of structures and forced more than 60,000 residents — roughly 10% of the local population — to evacuate. Three major blazes have consumed over 8,000 acres and remain uncontained, with 17 fires active across Washington state as of Monday, according to state Public Lands Commissioner Dave Upthegrove.

The devastation in the Pacific Northwest is not an isolated event. Greece is battling fires that have burned tens of thousands of acres and triggered mass evacuations. These follow the historic blazes that swept France and Spain last month, displacing hundreds of thousands. The fires erupted in different regions and ecosystems, but climate scientists point to a single underlying driver: rising global temperatures are worsening wildfire risk through two distinct mechanisms operating simultaneously.

First, traditional fire country is becoming hotter and drier across all regions. Second, the range of landscapes capable of sustaining destructive blazes is expanding into areas that historically rarely stayed hot and dry long enough to support large fires. Noah Diffenbaugh, a professor of Earth system science at Stanford University, describes global warming as "putting a thumb on the scale, producing severe and unprecedented heat waves" that progressively dry out trees and vegetation over extended periods, turning forests that evolved under cool, moist conditions into combustible tinderboxes.

Research published last month by a team including Boise State University wildfire researcher Mojtaba Sadegh identified "fire weather waves" — prolonged episodes of exceptionally hot, dry and often windy weather. The study found that between 1979 and 2024, such waves occurred on just 4% of days globally but coincided with more than a quarter of all land area burned and nearly half of the most energetic forest fires. These episodes have become more frequent in most regions since 1979, and the trend is projected to continue.

Why the Fire Risk Map Is Being Redrawn

The Two Mechanisms Expanding Exposure

Daniel Swain, a University of California climate scientist, frames the shift as a dual expansion: fire-prone areas are getting worse, while entirely new landscapes are crossing a flammability threshold. The latter is particularly significant for insurers because it means properties in regions not historically priced for wildfire risk may now face genuine exposure. Forests in Canada's boreal zone, California's Sierra Nevada, and temperate Europe were simply not adapted for the sustained heat and dryness now occurring — unlike the American Southwest, where ecosystems evolved with seasonal drought and frequent fire.

Fire Weather Waves and the Catastrophe Modelling Challenge

The fire weather wave concept has direct implications for how insurers model aggregate risk. If a small fraction of days drives a disproportionate share of burned area, traditional annualised or seasonal risk averages may understate tail risk. The finding that these clustered extreme periods are becoming more frequent in most regions suggests that historical loss data — already a limited guide in a changing climate — may increasingly misrepresent current probabilities. For reinsurers and primary carriers with concentrated property exposure in the wildland-urban interface, this clustering effect matters for capital allocation and treaty pricing.

Mutual Aid Constraints and the Global Simultaneity Problem

The article highlights a practical consequence that has insurance ramifications: when fires occur everywhere at once, nations cannot easily dispatch firefighting aircraft and personnel to assist one another. This simultaneity means a bad fire season in one region is less likely to be offset by quiet conditions elsewhere — a dynamic that challenges the geographic diversification assumptions embedded in many property reinsurance programmes. The snow drought last winter across the Pacific Northwest, Rocky Mountains, and parts of California further compounds the problem, robbing landscapes of the gradual spring snowmelt that normally keeps vegetation and trees hydrated into early summer.

Communities Facing Unanticipated Risk

The expanding geography of fire susceptibility means communities that never considered themselves at risk are now being told to prepare evacuation plans and fire mitigation measures. This has a direct insurance consequence: property owners in these newly vulnerable zones may lack both the physical protections and the coverage appropriate to their actual risk level. Sadegh's comparison of heat wave effects on vegetation to the cumulative toll of successive hot days on the human body underscores that risk accumulates non-linearly — a dynamic that linear pricing models may fail to capture.

What the New Fire Reality Means for Underwriters and Property Owners

The findings point to several concrete implications for insurance professionals and the property owners they serve:

• Re-examine exposure maps for regions newly crossing the flammability threshold. The research indicates that temperate forests in Canada, the Sierra Nevada, and parts of Europe — ecosystems not historically priced for frequent large fires — are becoming susceptible. Portfolios with concentrations in areas adjacent to wildland vegetation that were previously considered low-risk may need recalibration, particularly where snow drought has starved trees of moisture heading into fire season.
• Assess catastrophe models for fire-weather-wave clustering. The finding that 4% of days drive over 25% of burned area means tail-risk scenarios may be understated in models built on smoothed annual averages. Underwriters should ask whether their vendor models capture the temporal clustering identified in Sadegh's research and whether assumed diversification benefits hold when fires occur simultaneously across regions.
• Factor in mutual-aid constraints during multi-region events. The simultaneity problem — fires burning everywhere at once limiting cross-border firefighting support — means expected loss mitigation from aerial suppression may be overstated in peak scenarios. This has implications for both gross loss estimates and for reinsurance programmes that assume regional fire activity is largely uncorrelated.
• Engage policyholders in newly exposed areas about mitigation. The article notes that communities which never thought they needed evacuation plans or fire mitigation must now reassess. For insurers, this is a window to provide guidance on defensible space, ember-resistant construction, and evacuation readiness — measures that can materially reduce loss severity even as the underlying hazard grows.