In a particularly stark symptom of this trend, which is affecting more than 143 million Americans, Lake Mead - the country's largest reservoir, lying at the border of Nevada and Arizona - now stands at its lowest level since its creation in the 1930s. Authorities expected something like this - but not until August. The situation in northern California, which normally receives ample precipitation in the winter and spring, is no better. Lake Oroville, the state's second largest reservoir and a key part of a network providing potable water to 27 million Californians, is 165 feet (50 meters) lower than in 2019.

Widespread water-use restrictions appear inevitable over the coming months, with potentially serious ramifications for Western states, in particular for irrigation-dependent farmers - who provide much of the country's fruits and vegetables. In California, whose vast almond groves supply 80 percent of world production, some farmers have already begun uprooting trees to save water.

According to the US Drought Monitor, one third of California is currently experiencing "exceptional drought," the worst level. And dry soils and water-deprived vegetation create the conditions for even higher temperatures, feeding a devastating vicious circle. Authorities are particularly concerned about forest fires, which have arrived unusually early this year and with rare intensity. As of the end of May, fires in California had already destroyed five times as much vegetation as they had last year at this point.