A lack of winter snow cover and ongoing drought primed vegetation in these states for ignition. But in recent weeks, another ingredient for extreme wildfire emerged: heat. High temperatures dry out vegetation and decrease the relative humidity, making it easier for fires to ignite and spread.
Areas with warmer than average temperatures are shown in red; near-normal temperatures are white; and areas that were cooler than the 2000-2011 base period are blue. Colorado experienced the brunt of the heat wave and had eight large wildfires burning on June 28, 2012. Wyoming and Utah—other states that have seen unusually hot weather—together had nine wildfires burning.