Watch vs. warning vs. advisory
The National Weather Service uses three main alert levels. The words are short, but they ask for very different responses: a watch means get ready, a warning means act now, and an advisory means be careful.
| Level | What it means | What to do | Typical lead time |
|---|---|---|---|
| Warning | The hazard is happening, or is about to, and threatens life or property. | Take protective action now. | Minutes (tornado) to a day or two (winter storm) |
| Watch | Conditions are favorable for the hazard. It may or may not happen. | Review your plan and stay alert for warnings. | Hours to two days |
| Advisory | Less serious weather that is still a nuisance and can be dangerous if you are careless. | Use caution, especially when driving. | Hours to a day |
Tornado watch vs. tornado warning
A tornado watch covers a large area, often parts of several states, for four to eight hours when the atmosphere could produce tornadoes. It is issued by the Storm Prediction Center. A tornado warning is issued by your local forecast office for a specific storm when a tornado is seen or radar shows rotation. A watch means "it could happen today"; a warning means "it is happening near you, take shelter".
An easy way to remember it: during a watch the ingredients for a cake are on the counter; during a warning the cake is in the oven.
Winter storm watch vs. warning vs. advisory
A winter storm watch is issued a day or two before a storm that could bring heavy snow or ice. It becomes a winter storm warning when forecasters are confident it will reach local warning criteria, or a winter weather advisory if the storm looks weaker but will still make roads slippery. Winter alerts are explained in detail here.
Flood watch vs. flood warning vs. flash flood warning
A flood watch means heavy rain could lead to flooding. A flood warning means flooding is happening or imminent, often along rivers and lasting a day or longer. A flash flood warning is the urgent one: water is rising quickly, usually within hours of heavy rain, and you should move to higher ground immediately.
Other alert words you will see
- Statement: information about weather that does not meet advisory level, such as a special weather statement about a strong storm.
- Emergency: the most severe form of a warning, such as a tornado emergency or flash flood emergency, used when a catastrophe is underway in a populated area.
- Outlook: a forecast of possible hazardous weather several days ahead, such as the Storm Prediction Center's convective outlooks.