Severe thunderstorm risk categories: What do they mean?

Gray clouds and storm wall was seen moving into south Kettering Friday morning on June 18, 2021. SUSAN CARROLL / STAFF

Gray clouds and storm wall was seen moving into south Kettering Friday morning on June 18, 2021. SUSAN CARROLL / STAFF
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Updated April 13, 2022
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From lightning and flooding to hail and 50 mile-per-hour winds, thunderstorms can come with different risks and levels of severity.

The National Weather Service defines a severe thunderstorm as having wind gusts to at least 58 mph, hail at least a half-inch diameter or a having a tornado.

ExploreSevere weather safety: How you can prepare for severe thunderstorms, tornadoes
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To help people understand the different safety hazards, the NWS uses risk categories from marginal to high.

Here’s what the different categories mean:

  • Marginal: Isolated severe thunderstorms possible; limited in duration and/or coverage and/or intensity.
  • Slight: Scattered severe storms possible; short-lived and/or not widespread; isolated intense storms possible.
  • Enhanced: Numerous severe storms possible; more persistent and/or widespread; a few intense.
  • Moderate: Widespread severe storms likely; long-lived, widespread and intense.
  • High: Widespread severe storms expected; long-lived, very widespread and particularly intense.

Regardless of the risk categories, all thunderstorms have a threat of lightning and flooding.

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