The National Climate Assessment states, “Hotter and drier weather and earlier snowmelt mean that wildfires in the West start earlier in the spring, last later into the fall, and burn more acreage.”
- Southeast: The southeastern US (including Texas and Oklahoma) leads the nation in number of wildfires, averaging 45,000 fires per year, and this number continues to increase. Increasing temperatures contribute to increased fire frequency, intensity, and size, though at some level of fire frequency, increased fire frequency would lead to decreased fire intensity. Lightning is a frequent initiator of wildfires, and the Southeast currently has the greatest frequency of lightning strikes of any region of the country. Increasing temperatures and changing atmospheric patterns may affect the number of lightning strikes in the Southeast, which could influence air quality, direct injury, and wildfires.
- Northwest: A 2006 study found a statistically significant relationship between warming in the North Pacific and all the major wildfire events in the northwestern US from 1980-2002.
- Alaska: A 2016 attribution analysis indicated that Alaskan fuel conditions during the 2015 fire season were 34%–60% more likely to occur in today’s anthropogenically changed climate than in the past.
- Great Plains: A 2017 study found that the total area burned by large wildfires in the Great Plains rose 400% over a three-decade study period (1984-2014). The study also found that the average number of large wildfires in the biome increased from 33.4 ± 5.6 per year from 1985 to 1994 to 116.8 ± 28.8 wildfires per year from 2005 to 2014.
- West: According to the US National Academy of Sciences, over the past 30 years, there has been a fourfold increase in the number of large and long-duration forest fires in the American West. The length of the fire season has expanded by 2.5 months, and the size of wildfires has increased severalfold. Additionally, more than half the US Western states have experienced their largest wildfire on record since 2000. For California-specific information, see the California Increased Wildfire Risk signal page.
A global analysis of daily fire weather trends from 1979 to 2013 shows that fire weather seasons have lengthened across 29.6 million km2—or 25.3 percent—of the Earth’s vegetated surface, resulting in an 18.7 percent increase in global mean fire weather season length.