Drought Expands across the United States | NASA Earth Observatory

Drought Expands across the United States | NASA Earth Observatory

Unusually dry conditions gripped over half the contiguous United States in October 2024. On October 29, abnormal dryness and drought affected over 78 percent of the American population—the highest percentage in the U.S. Drought Monitor’s 25-year-long record.

Drier- and warmer-than-normal weather dominated the country during much of October, caused by a strong ridge of high pressure that lingered high in the atmosphere for weeks. According to the Southeast Regional Climate Center, 100 weather stations across the U.S. recorded no rain in October, including the cities of Philadelphia, Atlanta, Birmingham, Dallas, Las Vegas, and Sacramento. Over 70 weather stations recorded the driest October on record.

This map shows conditions in the contiguous U.S. on October 29, 2024, as reported by the U.S. Drought Monitor, a partnership of the U.S. Department of Agriculture, National Oceanic and Atmospheric Administration (NOAA), and the University of Nebraska-Lincoln. The map depicts drought intensity in progressive shades of yellow to red. It is based on an analysis of climate, soil, crop, and water condition measurements from more than 350 federal, state, and local observers around the country. NASA contributes several measurements and models that aid the drought monitoring effort.

Drought had expanded from covering just 12 percent of the country in June to 54 percent as of October 29. The rapid development created what NOAA describes as a “flash drought” in many parts of the country. Flash droughts are typically brought on by lower-than-normal rates of precipitation, accompanied by abnormally high temperatures, wind, or radiation.

“Although droughts usually develop slowly over the course of months and years, a flash drought rapidly intensifies over the course of a few weeks to a couple of months,” said Caily Schwartz, a scientist at the Global Water Security Center at the University of Alabama. Schwartz noted that in Nebraska, where the National Drought Mitigation Center is located, there has been little rain and higher-than-normal temperatures in October. Much of the state was in severe drought (represented as orange in the map) in late October.

Almost the entire country was warmer than normal the week of October 23-29, and drought was present in every state except Alaska and Kentucky. The High Plains and South were the warmest regions, with temperatures 10 to 12 degrees Fahrenheit (6 to 7 degrees Celsius) above normal.

Even in the Southeast where Hurricane Helene dropped significant precipitation in late September, many places dried out rapidly, with some recording zero precipitation since the hurricane.

“This fall has been a prime example of flash drought across parts of the U.S.,” said Jason Otkin, a meteorologist at the University of Wisconsin-Madison. “These events can take people by surprise because you can quickly go from being drought-free to having severe drought conditions.”

Otkin co-authored research published in Science that showed that droughts have intensified more rapidly since the 1950s due to human-caused climate change. According to the research team, flash droughts have become more common over much of the world, making drought monitoring and forecasting more difficult.

Read Science journal article "A global transition to flash droughts under climate change":

https://www.science.org/doi/10.1126/science.abn6301

Image Credit: NASA Earth Observatory image by Michala Garrison, using data from the United States Drought Monitor at the University of Nebraska-Lincoln

Article Credit: Emily Cassidy

Release Date: Nov. 2, 2024

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