Why Severe Storm Risk Is Rising — And The Regions Seeing The Biggest Shift

A warming climate is increasing the potential for severe thunderstorms across the country, especially during the spring months, according to a new analysis of more than 20 years of government climate data.

Conditions that support severe thunderstorms have become more frequent in recent decades, according to a Climate Central report linking the uptick to changes in “convective available potential energy.” CAPE, as it is called, is a key measure of atmospheric instability that contributes to the development of thunderstorms with the potential to produce tornadoes, damaging winds and hail.

The most significant increases are occurring during the traditional severe weather season, from April through September, when the atmosphere is already volatile. As temperatures rise, warmer air holds more moisture, providing additional fuel for thunderstorms. That added energy can translate into stronger updrafts, heavier rainfall, and more damaging winds.

Climate Central’s analysis of National Oceanic and Atmospheric Administration data from 1979 to 2021 shows that springtime — already peak tornado and severe storm season — is seeing a notable uptick in high-CAPE days, signaling greater storm potential.

Such storms accounted for nearly half of all billion-dollar weather disasters in the United States since 1980, according to data from NOAA’s National Center for Environmental Information.

Midwest, Ohio Valley, South See Uptick

The increase in thunderstorm potential is strongest across parts of the Midwest, Ohio Valley and South.

Since 1979, some areas — including Kentucky, Tennessee and the central Ohio Valley — have experienced 10 to 15 more days each spring with high instability, a key ingredient for severe storms.

This aligns with broader research showing that the geography of severe weather risk is gradually shifting eastward, away from the traditional Great Plains “Tornado Alley” and toward more densely populated regions of the Midwest and Southeast.

Central U.S.: More Intense Wind

Thunderstorms are not just becoming more likely in the nation’s midsection; they’re becoming more intense.

Thunderstorm wind speeds in the central U.S. have increased by about 7 percent for every 1 degree Fahrenheit of warming between 1980 and 2020, according to the data.

At the same time, the geographic area affected by damaging thunderstorm winds has expanded dramatically, increasing the potential for widespread power outages and infrastructure damage.

Northeast Faces Rising Risk

In the Northeast, including areas like New York and New England, trends are more variable but still trending upward overall.

While the region doesn’t see the same magnitude of increase as the Midwest or South, rising humidity and warmer temperatures are contributing to more frequent days with storm-friendly conditions. Scientists say episodic but potentially intense and severe weather events could become more common.

Minimal Change In West

California remains relatively stable and low-risk compared to the rest of the country when it comes to increasing severe thunderstorm potential. Even with warming temperatures, there generally isn’t enough humidity to significantly boost thunderstorm fuel in most of the state. Northern and mountainous regions may see strong storms at times, the report notes.

The report shows modest increases in instability in some inland areas, especially east of the Cascades. Coastal zones are expected to remain cool and stable, suppressing thunderstorm development.

More Monsoon Potential In Southwest

The pattern is more nuanced in the Southwest, including Arizona, New Mexico and parts of Nevada. The report shows signs of increasing atmospheric instability during the summer monsoon season, especially when moisture surges northward from the Gulf of California and eastern Pacific.

Outside the monsoon season, which typically runs from mid-June to the end of September, conditions will be too dry for widespread storm development, the data suggests.

Mixed Signals In Rockies, Interior West

The report shows patchy or inconsistent in the Rocky Mountains and interior West. Thunderstorms may develop in higher elevations with daytime heating, but moisture variability limits long-term increases in thunderstorms.

Some areas may see slight increases in storm-friendly days, while others show no clear trend or even decreases, the report says.

A More Volatile Future

Researchers caution that more favorable conditions for thunderstorms don’t always translate directly into more storms. Other atmospheric factors, such as wind shear, also play a role.

Still, the overall signal is clear: A warming climate is loading the dice toward stronger and more damaging storms.

“Warm, rising air is central to the formation of thunderstorms,” the report notes, and increases in atmospheric instability are expected to raise the risk of severe weather and related damage in the years ahead.

For communities across the United States, especially in the Midwest and Southeast, the findings suggest that severe weather preparedness may need to evolve alongside a changing climate.