Fueled by climate change, the first major heat wave of the summer has seized the western United States, toppling records and threatening lives. The event is unprecedented in its timing, intensity and scope, said Washington State University climate scientist Deepti Singh; never have such severe conditions been recorded over such a large area so early in the summer.
The persistent lack of moisture amplifies already scorching conditions, scientists say. The energy required to turn water into vapor usually brings down temperatures — that’s why evaporating sweat helps cool a person off.
“But right now, because of how dry it is, all that energy is just going into heating our atmosphere and heating the surface,” Singh said.