Weather Alerts
What Is a Severe Thunderstorm Warning?
A Severe Thunderstorm Warning means severe criteria have been observed or indicated for a defined area and time window.
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Quick answer / What to check next
Quick answer
A severe thunderstorm warning is an official alert indicating that a severe thunderstorm is occurring or imminent in the warned area.
What this signal means
Severe storms can disrupt power, aviation, outdoor events, road travel, and communications even when they are not part of a larger outbreak.
What to check on HazardNow
Warning polygon, counties or zones, expiration time, and update statements.
Verify with official source
National Weather Service
Quick read
- Useful for
- Identifying damaging wind or hail threats that may change quickly.
- Watch
- warning polygon, expected hazards, radar indication vs. spotter report, and expiration time.
- Confirm with
- NWS warning text and local NWS updates.
- Remember
- A warning can include serious wind and hail even when no tornado warning is active.
What this warning actually means
The warning is usually based on radar signatures, trained spotter reports, or measured severe criteria such as large hail or damaging winds. The polygon shows the most relevant area, but the text often contains the clearest hazard and motion details.
Treat the issue time, storm movement, and expiration as part of the signal. A later update can shrink, expand, cancel, or continue the warning.
Visual reference
Thunderstorm warning anatomy
Warning text connects observed/indicated evidence to a moving polygon and a short valid time.
Official sources to verify
Use these links to verify current source text, update timing, and agency caveats.
Last reviewed: . This page explains general preparedness information and does not replace official instructions.
FAQ
Does a warning mean severe weather is happening now?
It generally means the hazard is occurring or imminent in the warned area. Read the official NWS product for exact wording and timing.
Can a severe thunderstorm warning include tornado risk?
Some severe thunderstorm warnings include tornado-related language, but tornado warnings are separate official products when issued.
Related terms
Check the live HazardNow dashboard
Use this page to understand Severe thunderstorm warning. Use the live dashboard to see current alerts, infrastructure stress, weather, wildfire, travel, public-health, supply-chain, and stability indicators in one place. Focus on weather-alerts, tornado-watch-vs-warning, airport-ground-stop in the live view.