What classifies a thunderstorm as ‘severe?’

Published: Mar. 28, 2023 at 12:44 PM CDT
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QUAD CITIES, Iowa/Ill. (KWQC) - Thunder, lightning, heavy rain. It’s estimated more than 100,000 thunderstorms occur each year in the United States. Of those, only 10% are classified as severe.

A severe thunderstorm is a thunderstorm capable of producing damaging winds of 58 mph or greater, and/or hail that is one inch in diameter or larger, that’s about the size of a quarter.

Depending on the speed of the thunderstorm’s updraft, hail can be larger than a softball. Fortunately that’s not too common in eastern Iowa and western Illinois.

The largest hailstone recorded on record in the US was 8 inches in diameter, occurring in Vivian, South Dakota on July 23, 2010; the hailstone weighed nearly two pounds.

Hail causes nearly $1 billion in damage to property and crops.

straight-line winds are responsible for most thunderstorm wind damage. Winds can exceed 100 mph, similar to what happened during the derecho on August 10, 2020.

Peak gusts were around 140 mph in Cedar Rapids, Iowa.

Locally, winds were generally between 50 to 85 miles per hour.

Severe thunderstorm outlooks are issued by the Storm Prediction Center, highlighting areas where severe weather is possible and it’s broken up into five different levels.

Severe Thunderstorm Risk Categories from the Storm Prediction Center.
Severe Thunderstorm Risk Categories from the Storm Prediction Center.(KWQC)

Anytime severe weather is in the forecast, the First Alert Weather team will issue a “First Alert Day” to keep you ahead of the storm.