Chapter 10 · Natural disasters
Watch, warning, and advisory: what each alert means
The National Weather Service (NWS) uses the same three levels for almost every hazard. Alerts on your phone usually arrive in English: learn to recognize the key word.
| Level | Meaning | What you do |
|---|---|---|
| Advisory | The hazard will cause inconvenience; it can be dangerous if you aren't careful. | Use caution, stay informed. |
| Watch | Conditions are favorable. It may happen; it's not certain. | Get ready: review your plan, your kit, and your shelter. Charge phones. Have your shoes ready. |
| Warning | It is happening, is imminent, or has been detected by radar. | Act immediately: take shelter, move to high ground, or evacuate as appropriate. |
| Hazard | Watch | Warning |
| Tornado | Tornado Watch: tornadoes are possible in the area. It covers several counties. | Tornado Warning: a tornado has been seen or indicated by radar. It covers an area the size of a city. Go to your shelter now. |
| Flash flood | Flood Watch: conditions favor flooding. | Flash Flood Warning: flooding is imminent or happening. Move to high ground now. It can happen even if it isn't raining where you are. |
| Severe thunderstorm | Severe Thunderstorm Watch | Severe Thunderstorm Warning: hail 1 inch (2.5 cm) or larger and/or winds of 58 mph (93 km/h) or more. Go inside and stay away from windows. |
| Heat | Extreme Heat Watch | Heat Advisory or Extreme Heat Warning (formerly "Excessive Heat," renamed in March 2025). |
| Cold | Extreme Cold Watch | Cold Weather Advisory or Extreme Cold Warning (they replaced the "Wind Chill" alerts in October 2024). |
| Winter storm | Winter Storm Watch | Winter Storm Warning or Ice Storm Warning. |
| Hurricane | Hurricane Watch: winds of 74 mph (119 km/h) or more are possible; about 48 hours before tropical-storm-force winds. | Hurricane Warning: winds of 74 mph or more are expected; about 36 hours before. Finish your preparations. |
| Tropical storm | Tropical Storm Watch: winds of 39 to 73 mph (63 to 117 km/h) possible within 48 hours. | Tropical Storm Warning: those winds are expected within 36 hours. |
| Fire | Fire Weather Watch | Red Flag Warning: wind, dryness, and low humidity make any spark turn into a wildfire. Do not build fires outdoors. |
