NWS: Understanding Severe Thunderstorm Risk Categories


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The above graphic from the National Weather Service defines Severe Thunderstorm Risk Categories.

Thunderstorms – No severe* thunder storms expected
Lightning/flooding threats exist with all thunderstorms

  • Winds to 40 mph
  • small hail

1 – Marginal (MRGL) - Isolated severe thunderstorms possible
Limited in duration and/or coverage and/or intensity

  • Winds 40-60 mph
  • Hail up to 1″
  • Low tornado risk


2 – Slight (SLGT) – Scattered severe storms possible
Short-lived and/or not widespread, isolated intense storms possible

  • One or two tornadoes
  • Reports of strong winds/wind damage
  • Hail ~ 1″, isolated 2″


3 – Enhanced (ENH) – Numerous severe storms possible
Numerous severe storms possible

  • A few tornadoes
  • Several reports of wind damage
  • Damaging hail, 1-2″


4 – Moderate (MDT) – Widespread severe storms likely
Long-lived, widespread and intense

  • Strong tornadoes
  • Widespread wind damage
  • Destructive hail, 2″+


5 – High (HIGH) – Widespread severe storms expected
Long-lived, very widespread and particularly intense

  • Tornado outbreak
  • Derecho

* NWS defines a severe thunderstorm as measured wind gusts up to and at least 58 mph and/or hail to at least one inch in diameter, and/or a tornado. All thunderstorm categories imply lightning and the potential for flooding. Categories are also tied to the probability of a severe weather event within 25 miles of your location.


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