Watch or warning: the difference
These two words carry more weight than any other pair in American weather, and they are routinely swapped. The distinction is simple, and it is about time.
The one-line version
A watch means conditions are favourable for dangerous weather. It is issued in advance, often hours ahead, and it covers a large area. Be ready.
A warning means the dangerous weather is happening or is about to happen. It is issued for a small area and a short time. Act now.
An advisory sits below both. Conditions are expected that are inconvenient and can be hazardous, but that are not life-threatening for most people if reasonable care is taken.
Why the shape of each is different
A watch is drawn broadly because forecasters know the ingredients are coming together over a region but not yet where a storm will form. A warning is drawn tightly, often as a polygon covering parts of a county or two, because by then there is a specific storm on radar or a specific report on the ground.
This is why a watch can last for hours and a warning usually lasts under an hour. They are answering different questions.
What to do with each
During a watch, decide in advance what you would do. Know where your shelter is, charge what needs charging, and make sure you will actually be woken if something is issued overnight. A watch is time you are being given.
During a warning, do the thing. Warnings are short because the window is short, and the actions are specific to the hazard: an interior room on the lowest floor for a tornado, away from water for a flash flood, off the road and out of a vehicle for the worst of a severe thunderstorm.
Common questions
- Which is more serious, a watch or a warning?
- A warning. A watch means conditions are favourable for dangerous weather; a warning means it is happening or imminent and you should act immediately.
- How long does a warning last?
- Usually less than an hour, because it covers a specific storm affecting a specific small area. Watches typically run for several hours over a much larger region.
- What is a weather advisory?
- An advisory covers conditions that are inconvenient and potentially hazardous but generally not life-threatening if reasonable care is taken. It sits below a watch and a warning.
Every active National Weather Service alert, rendered exactly as issued.
Related guides
- What a Slight Risk actually means
- What the colors on a weather radar mean
- Heat Advisory or Extreme Heat Warning: what each one means
Categories and definitions on this page follow the National Weather Service and the Storm Prediction Center. For the official text of any product in effect, see weather.gov.