40 weeks and counting: This chart shows the severity of the U.S. drought

A major heatwave is affecting the Pacific Northwest of the United States, but the stretch of unusually hot and dry weather is just the latest addition to drought conditions the country has been experiencing since late 2020. The extreme circumstances have spurred demand for water and cooling, while leaving reservoirs emptier than usual. With the drought comes a heightened risk of heat-induced medical emergencies and wildfires. According to the U.S. Drought Monitor, extreme and exceptional drought affected the Southwest strongest, but also stretched into Oregon, Washington, North Dakota and Texas.

As of this Monday, droughts of different levels of severity affected almost 61 percent of the area of the continental United States. The number has been hovering around the 60-percent mark since September of 2020 or for 40 weeks total. While the number has risen as high before, it rarely stayed there for so long. During the drought of 2018, it exceeded the threshold for only five weeks.

The last time a major drought in the U.S. lasted for so long was between April 2012 and May 2013, when droughts affected more than 60 percent of the United States’ area for 60 weeks in a row and expanded to around 80 percent momentarily. But even during that time, the area classified as under exceptional drought never exceeded 7 percent. In the current scenario, it has been consistently above 8 percent for 31 weeks, most recently approaching 10 percent.

While fluctuating temperatures and very hot, very dry or very cold days are a normal phenomenon, these extreme weather events are expected to become more frequent and severe due to climate change. Scientist have connected the reoccuring drought in the Western U.S. to a changing climate, for example citing heatwaves that start earlier in the year and have become longer as well as stronger.