It's the Peak Time For Destructive Thunderstorm Winds in the United States

Chris Dolce
Published: June 11, 2019

We are amid the annual peak for damaging wind reports from severe thunderstorms across the United States.

June and July have both averaged close to 3,000 severe wind reports annually during the past 19 years, according to data compiled by NOAA's Storm Prediction Center.

A thunderstorm can produce a severe wind report if there's a measured wind gust of 58 mph or greater or if there are reports of damage to structures, trees and power lines caused by straight-line winds.

Average number of severe wind/damaging wind reports from thunderstorms May-August during 2000-2018. There is a peak in the number of reports during June and July.

You can see on the graph how the average number of reports from June and July stands well above the next closest months of May and August. All other months see substantially lower severe wind reports overall compared to May-August.

June 2008 (5,445 reports) and July 2017(4,642 reports) are the months with the most severe wind reports dating back to 2000. June and July are the only months that have logged more than 4,000 severe thunderstorm wind reports.

The reason for the June and July peak is fairly straightforward: Moisture and warm temperatures are most widespread and abundant east of the Rockies during this time of year, making conditions hospitable for thunderstorm development everywhere.

The jet stream, which flows from west-to-east near the Canadian border in summer, sends disturbances over top of this moisture and fuels thunderstorm development throughout the nation's northern tier.

In the South, daytime heating of the moist atmosphere leads to isolated or scattered pop-up thunderstorm development most days. The Desert Southwest gets into the mix in July as annual monsoon moisture makes its way into the region, causing thunderstorms to form more frequently.

Any of those thunderstorms can produce a downburst that causes wind damage in a small area on a given day. 

An example of a Mesoscale Convective System (MCS) as viewed from colorized infrared satellite imagery. These thunderstorms complexes can produce swaths of wind damage, including derechos. (GOES-16 experimental image from July 10, 2017)

Sometimes thunderstorm complexes called mesoscale convective systems (MCS) impact the Plains, Midwest and East with more widespread swaths of wind damage in summer.

Occasionally, an extreme version of an MCS called a derecho will develop, affecting a widespread area hundreds of miles long with severe wind damage. Derechos are an infrequent event overall for any given location, but they most commonly occur from parts of the southern Plains into the upper and mid-Mississippi Valley and Ohio Valley.

Derechos can down numerous trees and lead to major power outages for days in the middle of summer. An extreme example occurred on June 29, 2012 when a derecho spread more than 600 severe thunderstorm wind reports from the Ohio Valley into the mid-Atlantic regions. It was dubbed a "superderecho" by some because of how widespread the impacts were.

The map above shows where derechos most commonly occur.
(NOAA's Storm Prediction Center)

Although you should always be alert for damaging thunderstorms year-round, the summer months can be particularly dangerous with more people outdoors and in harm's way when it's warmer.

Severe thunderstorm winds in the United States led to the deaths of 24 people in 2018, 30 in 2017 and 20 in 2016, according to NOAA. Both 2018 and 2016 had more deaths from severe thunderstorm winds than tornadoes.

Be sure to have a way to get real-time weather alerts and don't ignore severe thunderstorm warnings when they are issued.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.