Severe storms are thunderstorms that produce tornadoes, damaging winds (58 mph or higher), and/or hail at least one inch in diameter.
Severe storms cause 200 deaths annually in the U.S. and account for nearly half of all billion-dollar weather disasters that have impacted the nation since 1980.
Every U.S. region faces severe weather risks—but especially in the Great Plains from April to July. People living in mobile homes are particularly vulnerable during high wind events.
Severe storms are localized, short-lived events with limited historical records, which makes it difficult to link their occurrence to global climate change. Here’s what we do know:
Tornado Trends. The number of tornadoes each year hasn’t changed since 1970 (when excluding the weakest events). But tornado variability has increased, concentrated in fewer outbreaks of larger magnitude. And tornado risk may be shifting eastward. There’s no clear connection between these observed trends and climate change, however.
Future Potential. Severe storms are more likely to form under certain conditions—including high convective available potential energy and wind shear. Studies suggest that conditions favorable to severe thunderstorms will become more frequent with warming over the 21st century—about 5-20% more frequent per 1.8°F of warming. But whether these changing conditions will ultimately result in more severe storms remains an active area of research.
These resources explore the science, trends, and local impacts of severe weather in the U.S.
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