Tell a watch, warning and advisory apart, with NWS thresholds for floods, heat, wind, storms, fire and cold

The three levels

A watch is issued when a hazard is possible. A warning is issued when it is occurring or imminent. An advisory is for conditions that are less serious. For example, the NWS issues a Winter Weather Advisory for events expected to cause a significant inconvenience but not serious enough to warrant a warning.

Flood watch vs flood warning vs advisory

A Flood Watch means conditions are favorable for flooding. It does not mean flooding will occur, but it is possible. A Flood Warning is issued when flooding is imminent or occurring, and a Flash Flood Warning when flash flooding is imminent or occurring. River Flood Watches and Warnings apply to forecast points along a river. For coastal areas, a Coastal Flood Advisory is for minor or nuisance flooding, while a Coastal Flood Warning is for moderate to major flooding that poses a serious risk to life and property.

Heat advisory vs extreme heat warning

The NWS lists an Extreme Heat Watch (potential for dangerous heat within 24 to 48 hours), an Extreme Heat Warning, and a Heat Advisory for the lower range. Its page still mentions an Excessive Heat Warning in the text, so you may see either name. The heat index values in the table are those NWS Baltimore/Washington uses; other offices set their own, and an advisory or warning may be issued at lower values early in the season or during a multi-day heat wave.

Wind advisory vs high wind warning

A Wind Advisory is for sustained winds of 31 to 39 mph for an hour or more and/or gusts of 46 to 57 mph. A High Wind Warning is for sustained winds of 40 mph or higher for an hour or more or gusts of 58 mph or higher. These are the criteria for the Baltimore/Washington area.

Severe thunderstorm and tornado alerts

A Severe Thunderstorm Watch means severe thunderstorms are possible in and near the watch area; a Warning means they are occurring or imminent. A Tornado Watch means severe thunderstorms and tornadoes are possible. A Tornado Warning means a tornado is imminent, and the NWS says to seek safe shelter immediately. See our tornado safety guide for where to go.

Red flag warning

A Red Flag Warning alerts fire officials to potentially dangerous fire weather conditions within the next 12 to 24 hours. For Virginia and Maryland, NWS Baltimore/Washington issues it when relative humidity is below 30 percent, sustained winds are 20 mph or more, and 10-hour fuel moisture is below 8 percent.

Extreme cold warning

The NWS now calls the former Wind Chill Warning an Extreme Cold Warning and the former Wind Chill Advisory a Cold Weather Advisory. For Baltimore/Washington, a warning is for wind chill or temperature at or below -10 east of the Blue Ridge and -20 to the west.

Freeze and frost alerts

A Freeze Watch is issued when significant, widespread freezing temperatures are possible within 24 to 36 hours, and a Freeze Warning when they are expected. Both are issued in autumn until the end of the growing season and in spring when it is late enough to damage new plants and crops. A Frost Advisory is for minimum temperatures forecast at 33 to 36 degrees on clear, calm nights during the growing season.

Thresholds vary by office

The numbers above come from one forecast office. Other offices use different criteria, so rely on the text of the alert for your location and on your local NWS office.

Sources

• NWS Baltimore/Washington: Watch/Warning/Advisory Definitions

Reviewed by the Storm Incoming editorial team on October 27, 2026. Follow local emergency officials if their instructions differ.