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The U.S. just saw its busiest July for severe thunderstorms on record [1]

['Matthew Cappucci']

Date: 2023-08-02

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The severe weather season in the United States usually peaks in April and May, but this year it experienced a midsummer resurgence. Multiple large-scale thunderstorm outbreaks occurred during July and produced the most reports of severe weather in the United States on record during the month. Want to know how your actions can help make a difference for our planet? Sign up for the Climate Coach newsletter, in your inbox every Tuesday and Thursday. ArrowRight Of particular note was the number of reports of large, destructive hail — at least two inches in diameter. Hail is usually more prevalent early in the season when leftover frigid air from winter is still present at high altitudes. Yet the National Weather Service logged more reports of large hail last month than any other July on record, and the sixth-most in any month.

July will also be remembered for its swarms of tornadoes, which included the most intense twister to hit North Carolina during July and tornadoes that were spotted from O’Hare International and Midway airports in Chicago.

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The barrage of storms can be tied to the same overarching weather pattern that’s brought exceptional heat to the nation’s southern tier.

How active was the month?

July 2023 Month-In-Review



1. Most prelim July severe weather reports on record

2. Most prelim 2+" hail reports on record (6th for any month)

3. Most summer (JJA) 2+ inch hail reports on record (1 month to go)

4. Most July watches since '03

5. A slight risk or greater every day — NWS Storm Prediction Center (@NWSSPC) August 2, 2023

Here’s a look at the numbers for just how busy July was for severe storms:

June and July combined yielded 528 reports of hail larger than golf balls (two inches in diameter or greater) across the country. The previous record for an entire summer, defined as June, July and August, was 378 reports in 2009. It’s worth noting that bookkeeping only dates back to 2004 for hail reports, but it’s a remarkable number regardless.

There were exactly 150 tornado and severe thunderstorm watches issued, the most July watches since 2003.

Every day featured at least a level 2 out of 5 “slight” risk of severe weather drawn by the Storm Prediction Center.

There was a July record of 6,637 severe weather reports, connoting thunderstorm wind damage, gusts over 58 mph, quarter-size hail or tornadoes. Though records date back only to 2004, that still takes the top spot. The previous record holder was July 2016, which netted 5,642 reports.

There were 188 reports of hail two inches or more in diameter, also a record for July.

North Carolina also faced its strongest July tornado on record — an EF3 that hit northwest of Rocky Mount on July 19, damaging a Pfizer facility. It came amid a sneaky severe weather setup. While rotating thunderstorms were not initially expected, a subtle mesoscale convective vortex — a remnant of a weak low-pressure swirl left over from previous days’ storms — enhanced low-level twist. The tornado touched down more than six minutes before a tornado warning was issued, but no fatalities were reported.

What caused the storms?

July was dominated by a sprawling heat dome, or stagnant ridge of high pressure, that brought historic heat to much of the southern United States. Temperatures skyrocketed in the Desert Southwest, the southern Plains, along the Gulf Coast and in the Southeast. The jet stream, a river of swiftly moving winds in the upper atmosphere, crested up and around the heat dome.

Thunderstorms ordinarily form on the edge of heat domes, feeding off the clash of hot air beneath the dome and cooler air to the north. Said “ridge riders” tap into jet stream energy, mixing strong winds to the surface. They also can produce hail, flooding and occasional tornadoes.

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The northern and central Plains, the Great Lakes and the Northeast found themselves on the periphery of the heat dome, square in the “storm highway” of sorts. What made this month unusual was how many severe storm setups began with rotating supercells, which are the primary producers of big hail.

Hailstones in Lake Garda big enough to punch holes in the sun loungers. pic.twitter.com/jfeWGEBckc — Richie Oakley #andacyclist (@roakleyIRL) July 25, 2023

That was partly caused by the “flatness” of the heat dome. It spent much of the month squashed over the southern United States rather than expanding fully northward. Moisture was able to sneak north and pool against the Rockies, while a swift west-to-east jet stream interacted with that moisture to spawn severe storms.

That prolonged tornado season spread across the Central states, too. Most of the tornadoes have skirted major metropolitan areas, but a few came close — such as a twister that formed in sight of Denver International Airport on July 29.

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On July 12, 13 tornadoes were confirmed by the Weather Service in northeast Illinois, west of Chicago.

The view from Chicago Midway Airport as a tornado-warned storm pushed through moments ago.



Over 1.7 million people in the Chicago area were included within this tornado warning.



Video sent in by: Taylor Mobley#weather #tornado #stormhour #ilwx #wx pic.twitter.com/DO56S1lBza — Nash Rhodes (@NashWX) July 12, 2023

Heading into August

The heat dome looks to break down and shift west into August, which will allow a jet stream dip to form over the eastern United States. That will probably pull down cooler, drier air from Canada, reducing severe weather risk somewhat east of the Mississippi.

That said, that same overarching pattern could be more favorable for potential effects from tropical storms if any materialize over the Atlantic Ocean, which would introduce severe weather potential.

In the short-term, the coming week does look busy. The Storm Prediction Center is already eyeing potential severe weather on Saturday over the Plains, shifting toward the Mid-South and the Ohio Valley on Sunday. Storms could reach the Eastern Seaboard early next week.

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[1] Url: https://www.washingtonpost.com/weather/2023/08/02/july-severe-thunderstorms-weather-us/

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