Severe thunderstorm warning criteria

WARNINGS EXPLAINED

The hail and wind thresholds behind base, considerable and destructive warnings, and why only one of them sets off your phone.

Reviewed October 4, 2026. Sources are listed at the end of the page.

Severe thunderstorm warning criteria

Either the hail or the wind is enough to reach a level. See our hail size chart for every size from pea to softball.

Why only “destructive” sets off your phone

Most Severe Thunderstorm Warnings are base-level storms that damage trees and roofs in spots. Sending a phone alert for every one would train people to ignore them. Since August 2, 2021, the National Weather Service sends a Wireless Emergency Alert only when a warning carries the destructive tag: baseball-size hail or 80 mph wind, the kind of storm that can cause damage like a weak tornado.

That means a considerable-level storm with golf ball hail and 70 mph wind can hit your town without your phone making a sound. If you want to hear about every warning, use a NOAA Weather Radio or free warning alerts by email or Messenger.

Severe Thunderstorm Watch vs. Warning

A Severe Thunderstorm Watch comes from the Storm Prediction Center when conditions favor severe storms over a large area for several hours. A Severe Thunderstorm Warning comes from your local forecast office when a storm is producing, or about to produce, severe hail or wind. The same pattern applies to tornadoes: see tornado watch vs. warning.

Severe thunderstorms can also produce tornadoes with little notice. Warnings for them sometimes include the phrase “tornado possible.” Treat that as a reason to stay near your shelter.

What to do in a severe thunderstorm warning

• Get inside a sturdy building and stay away from windows. Hail and flying debris break glass.
• Move cars under cover only if you can do it before the storm arrives. Do not go outside once hail starts.
• Treat 70–80 mph wind like a weak tornado. At considerable or destructive levels, go to the same interior room you would use for a tornado.
• Avoid driving into the storm. Heavy rain and hail can cut visibility to near zero. Never drive through a flooded road.
• Expect power outages. Have a flashlight and a charged battery ready. Our storm prep checklist covers the basics.

Questions people ask

Keep reading

Sources

1. National Weather Service, Severe Thunderstorm Warnings with destructive damage threat to trigger Wireless Emergency Alerts.
2. National Weather Service Chicago, New NWS thunderstorm damage threat categories.
3. National Weather Service Jackson, MS, Severe weather product guide.