Death Valley—the hottest and driest place in North America—was recently the site of an extreme bought of rainfall and subsequent disastrous flooding. This intense rainfall is rare, but was one of major thousand-year rain events that the United States experienced over the past few weeks.
You know the vibes in Death Valley: The desert in Eastern California and National Park of the same name regularly reach temperatures over 100 degrees Fahrenheit (37 degrees Celsius). Naturally, rainfall is typically sparse in this area of the world, but on August 5, 1.46 inches (3.7 centimeters) of rain fell on Death Valley, according to NASA Earth Observatory. This amount of rain equates to 75% of the average annual rainfall, which is about 2 inches (5 centimeters). This rainfall has now been classified as a “thousand-year rainfall event.”
The fact that these heavy rains are called thousand-year rainfall events is actually a bit of a misnomer. By the name, you might be inclined to think that these episodes of rainfall only occur once in a millennium, but the name of these rain events refers to the probability that they will occur in a year: 0.1% chance, or 1 in 1,000. In other words, they could occur every year, but likely won’t.
“What was experienced in Death Valley was a heavy rain event that has a 1,000 year average recurrence interval,” said National Weather Service meteorologist Dan Berc in an email to Gizmodo. “The associated flooding with this amount of rainfall can be devastating.”
What’s more concerning is that Death Valley’s particular squall was only one of four thousand-year rainfall events that the U.S. saw over the past few weeks. Rain in St. Louis on July 26, Kentucky on July 25 through July 30, and Illinois on August 2 were all thousand year rainfall events. As climate change continues to warm the planet, intense storms will become more common as a warmer atmosphere holds more water: The Intergovernmental Panel on Climate Change found in a 2021 report that heavy rain events will become 30% more frequent across the globe, and contain an average of 7% more water.