Tornado Watch vs Tornado Warning: the difference and what to do
One is issued from Oklahoma for a region and lasts hours. The other is issued from your local office for a polygon and lasts minutes. Here is who issues each, how much time you get, and what to do with it.
A Tornado Watch means the ingredients for tornadoes are in place over a region for the next several hours. A Tornado Warning means a tornado has been spotted or indicated by radar and is threatening a specific area now. The watch is the time to prepare; the warning is the time to act. Nearly 60,000 US searches a month ask about severe storms and tornadoes, and the watch-versus-warning confusion is the single most dangerous misunderstanding in American weather, because people wait for a "watch" to become serious.
Who issues what
- Tornado Watch: the NOAA Storm Prediction Center in Norman, Oklahoma, in coordination with the local forecast offices. Covers a large area, often several thousand square miles across multiple counties or states, and typically lasts 4 to 8 hours. A watch labelled PDS, Particularly Dangerous Situation, is reserved for expected outbreaks of strong, long-track tornadoes.
- Tornado Warning: your local NWS forecast office, drawn as a polygon around the storm's projected path, usually valid for 30 to 45 minutes. Warnings carry a damage-threat tag: base, considerable or catastrophic. A Tornado Emergency is the catastrophic tag with a confirmed violent tornado heading for a populated area; it is used a handful of times a year.
How much time you get
The average lead time on a tornado warning is around 10 to 15 minutes, and a fair share of tornadoes are warned with less or, for weak ones, none at all. That number is why the watch matters. During a watch you can move the car under cover, bring pets in, put shoes and a flashlight by the shelter, charge the phone and decide where the safe room is. During a warning, you have time for exactly one action: getting there.
Where to go
- House with a basement: the basement, under something sturdy, away from windows.
- House without a basement: an interior room on the lowest floor, a closet or bathroom, as many walls between you and outside as possible. Cover your head; most tornado injuries are from flying debris.
- Apartment: lowest floor you can reach, interior hallway or stairwell. Not the elevator.
- Mobile home: leave. Mobile homes account for a large majority of tornado deaths relative to their share of housing; any permanent building is safer, and the watch period is when to go.
- Car: a car is not a shelter. If a sturdy building is close, go to it. If not, stay belted, below window level, and never shelter under an overpass, where wind speeds increase. See is a car safe in a storm for the lightning side of the same question.
Reading the day before
Tornado days are usually flagged a day or two ahead by the Storm Prediction Center's outlook, where an Enhanced or Moderate risk with a hatched tornado area is the signal to take the next afternoon seriously. Our guide to the SPC severe weather outlook categories explains the colors and probabilities. The timing of the storms is the part forecast models argue over, and the argument matters: a line of storms arriving at 4 PM is a different threat from the same line at midnight, when tornadoes are twice as deadly because people are asleep. On our city pages, Oklahoma City or Memphis for example, the NWS blend, the American GFS and the European model sit side by side hour by hour. Our accuracy scoreboard shows which has been most reliable in your city, and once the storms are up the radar shows where they are.
Make sure the warning reaches you
Tornado Warnings are one of the few NWS products sent over Wireless Emergency Alerts, so a phone with alerts enabled will wake you. That is not true for most other hazards; how to get weather alerts on your phone covers what arrives, what does not, and the NOAA Weather Radio backup that works when the towers are down. The general grammar of the system is in watch vs warning, and what the difference means.