Temperatures and Wildfire Numbers in the U.S. West, 1970-2010. Across the U.S. West, the annual number of large wildfires has increased over the past 42 years, to varying degrees. climatecentral.org

Among the Western States, Arizona, California, Colorado, Idaho, and Montana have seen the most dramatic increases in wildfires since 1970. According to our analysis, the average annual number of large fires has nearly quadrupled in Arizona and Idaho, and at least doubled in California, Colorado, Montana, New Mexico, Nevada, Oregon, Utah, and Wyoming. On the other hand, the frequency of fires in Washington has remained steady.

Report: The Age of Western Wildfires [pdf]