Severe thunderstorms

What makes a storm severe?

Severe thunderstorms produce damaging wind, large hail or both. The usual warning thresholds are wind gusts of at least 58 mph or hail at least one inch across, roughly the size of a quarter. Lightning and flash flooding can also happen in storms that never receive a severe thunderstorm warning.

Choose shelter before the storm arrives

At home, go to an interior room away from windows. At school, work or an event, follow the shelter plan. A tent, picnic shelter or open garage is not a sturdy indoor shelter.

• Bring people and pets indoors before conditions worsen.
• Stay clear of windows that wind-blown debris or hail could break.
• Keep an alert source available while sheltering.

Thunder is your cue to stop outdoor activity

Do not wait for rain or an alert before responding to thunder. Go into a substantial building, or an enclosed vehicle with a metal roof if a building is unavailable. Avoid isolated trees, open shelters and water. Remain sheltered for at least 30 minutes after the last thunder.

Read each new warning

A storm can change as it moves. A later tornado or flash flood warning may require a different response. Check the hazard, affected locations and instructions instead of assuming the first alert describes the whole event.