Tornado Watch vs Warning

The difference between a tornado watch and a tornado warning is the difference between "get ready" and "go, now," and mixing them up costs precious minutes when a storm is bearing down. The two words sound almost interchangeable, but the National Weather Service uses them to mean very specific, very different things. What follows is what each term means and what it should prompt you to do.

What a tornado watch means

A tornado watch is issued when the atmosphere is primed for tornadoes, but none has formed yet. It is a heads-up, not an alarm. Watches are issued by the NOAA Storm Prediction Center in Norman, Oklahoma, where meteorologists monitor conditions across the entire country and flag areas where severe storms and tornadoes are likely to develop over the next several hours.

A watch covers a lot of ground, often a block of several counties or even parts of multiple states, and lasts a while, commonly 4 to 8 hours. If you are inside a tornado watch, the storms may still be hours away or may never reach you. The right response is to stay aware: keep a way to receive alerts, know where you would shelter, and be ready to move quickly if a warning follows.

What a tornado warning means

A tornado warning is the serious one. It means a tornado has been reported by trained spotters or indicated by Doppler radar, and there is a threat to life and property in the path of the storm. Warnings come from your local NWS forecast office, cover a much smaller area, sometimes a single town or a polygon drawn around the storm, and last a short time, often 30 to 45 minutes.

When a warning is issued for your location, the time for preparing is over. According to the National Severe Storms Laboratory, the safest place is a small, interior room on the lowest floor of a sturdy building, away from windows, with your head covered.

Watch vs warning, side by side

Why the difference matters

The two-tier system exists because forecasting a tornado works at two scales. Hours ahead, meteorologists can see that the atmosphere is loaded, the heat, moisture, and wind shear that feed rotating storms, but not exactly where or whether a tornado will drop. That is the watch. Minutes ahead, radar and spotters can pin down an actual, forming tornado. That is the warning. Collapsing the two into one alert would mean either crying wolf across whole states or giving people almost no notice. Keeping them separate lets a watch buy you preparation time and a warning buy you your life.

What to do when each is issued

During a watch: keep a charged phone with wireless emergency alerts turned on, or a NOAA Weather Radio nearby. Decide now where your shelter is, the lowest, most interior spot you can reach, and bring in anything you would not want to leave outside. If you are in a mobile home, identify a sturdier building you can get to fast, because mobile homes are not safe in tornadoes.

During a warning: go to your shelter immediately. Lowest floor, interior room, away from windows, head covered. If you are in a vehicle or a mobile home, get into a permanent structure if one is close; if not, follow the current guidance from local officials. Do not wait to see the tornado before acting, many are hidden by rain or darkness.

How the alerts reach you

Both watches and warnings are pushed through the same channels: NOAA Weather Radio, local TV and radio, weather apps, and Wireless Emergency Alerts, the loud tone-and-text messages that come to most cell phones automatically. Tornado warnings, and PDS-worded watches, are the ones that trigger those phone alerts. If you have ever silenced them, tornado season is the time to turn them back on.

The same watch-versus-warning split runs through the rest of severe weather. For thunderstorms and flash floods, a watch still means the setup is there and a warning still means it is happening. More of these are over in This vs That.