Over the last century in the Pacific Northwest, warm and dry conditions in any given year have generally led to larger fires and greater area burned. By decreasing fuel moisture and increasing the length of the fire season, warm and dry conditions create large areas of dry fuels that are more likely to ignite and carry fire over a longer period of time.
A warming climate will have profound effects on fire frequency, extent, and severity in the Pacific Northwest. Increased temperatures, decreased snowpack, and earlier snowmelt will likely lead to longer fire seasons, lower fuel moisture, higher likelihood of large fires, and greater area burned by wildfire. Interactions between fire and other disturbance agents (e.g., drought, insect outbreaks) will likely drive ecosystem changes in a warming climate. Increased tree stress and interacting effects of drought, insects, and disease may also contribute to increasing wildfire severity and area burned. Climatic changes and associated stressors will interact with vegetation conditions, as affected by historical land uses such as tree harvest and fire suppression, to affect fire regimes and forest conditions in the future.