Severe thunderstorm risk categories: What do they mean?

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

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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