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The analysis reveals a significant increase in fire weather days across much of the contiguous U.S., with the western U.S. experiencing far more frequent fire weather than the east. While the western U.S. has seen strong increases, particularly in the Southwest during spring and summer, parts of the eastern U.S. have also seen impactful increases, especially in the Southeast and Northeast. The study emphasizes that while human activity causes 87% of wildfires, fire weather primes the landscape for these fires to ignite and spread.

Climate Central's analysis of weather station data from 225 locations across 17 U.S. states reveals a significant increase in fire weather days since the 1970s, driven primarily by warming and decreasing relative humidity. The report highlights that interior regions have seen higher increases than coastal areas, with some parts of New Mexico experiencing two additional months of fire weather compared to nearly 50 years ago. Beyond increasing wildfire risk, these conditions have led utilities like PG&E to implement public safety power shutoffs (PSPSs) to prevent equipment-related ignitions, resulting in significant economic impacts and health risks. The document argues that while land management and localized grids can mitigate risk, long-term stabilization requires reducing carbon pollution to net zero by 2050.

The report concludes that the June 2021 Pacific Northwest heatwave was virtually impossible without human-caused climate change, estimating it as a 1-in-1000 year event in the current climate. The analysis indicates the event was approximately 2°C hotter than it would have been in a pre-industrial climate and would have been at least 150 times rarer without anthropogenic warming. Future projections suggest that in a world with 2°C of global warming, such an event would occur every 5 to 10 years and be another degree hotter. Meteorological drivers included an 'omega-block' high-pressure system and dry antecedent soil conditions, while natural variability modes like ENSO and PDO played little to no role.