Watch vs warning › Extreme heat watch vs warning
National Weather Service alert guide
Extreme heat watch vs warning
An extreme heat watch means conditions are favorable for an extreme heat event, but its timing is still uncertain. An extreme heat warning means extremely dangerous heat conditions are expected or occurring.
Heat kills quietly and it kills indoors. The people most at risk are older adults, small children, anyone working outside, and anyone without air conditioning.
What the National Weather Service says
Extreme Heat Watch
Issued when conditions are favorable for an extreme heat event but its occurrence and timing is still uncertain.
- Issued by
- Your local National Weather Service forecast office. The thresholds are set locally.
- How long it lasts
- The expiration time is written in the alert. Check it there.
Extreme Heat Warning
Issued when extremely dangerous heat conditions are expected or occurring.
- Issued by
- Your local National Weather Service forecast office. The thresholds are set locally.
- How long it lasts
- The expiration time is written in the alert. Check it there.
Heat Advisory
Issued for dangerous heat conditions that are not expected to reach warning criteria.
- Issued by
- Your local National Weather Service forecast office.
Some older material and some local coverage still say Excessive Heat Warning. The National Weather Service heat safety page now uses Extreme Heat Warning.
The National Weather Service does not publish one national temperature for these alerts on its heat safety page. Thresholds are set locally, because a temperature that is routine in one region is an emergency in another. Check the page for your local office.
These alerts are based on how hot it feels, which combines temperature and humidity, not on the thermometer alone.
What to do
If an extreme heat watch is issued
- Move outdoor work and outdoor plans to early morning, or move them to another day.
- Find out now where you would go if your home gets too hot. A cooling center, a library, a mall, or a relative's house.
- Check that your air conditioning works, or arrange somewhere to go.
- Make a list of people to check on. Older neighbors, anyone living alone, anyone without air conditioning.
- Start drinking water now rather than waiting until you are thirsty.
If an extreme heat warning is issued
- Stay out of the sun and stay somewhere with air conditioning.
- If your home has no air conditioning, go somewhere that does. A fan alone is not enough in extreme heat.
- Drink water through the day. Do not wait until you are thirsty.
- Cancel or move outdoor work and exercise. If you cannot, take frequent breaks in the shade and drink more.
- Wear light, loose clothing.
- Check on older neighbors, people living alone, and anyone without air conditioning. Do it in person.
- Never leave a child or a pet in a parked car, not even for a minute, not even with the windows cracked.
- Know the signs of heat stroke and what to do. They are listed below.
If a heat advisory is issued
- Take it seriously. Advisory heat is still dangerous heat.
- Move hard outdoor work to early morning.
- Drink more water than usual.
- Take shade breaks and stay in cool places when you can.
Common questions
What temperature is an extreme heat warning?
There is no single national temperature. The National Weather Service issues an Extreme Heat Warning when extremely dangerous heat conditions are expected or occurring, and each local forecast office sets the thresholds for its own area based on what people there are used to. Check your local National Weather Service office page for the numbers where you live.
Source: www.weather.gov/safety/heat-wwWhat is the difference between a heat advisory and an extreme heat warning?
A Heat Advisory is issued for dangerous heat conditions that are not expected to reach warning criteria. An Extreme Heat Warning is issued when extremely dangerous heat conditions are expected or occurring. Both are dangerous. The warning means change your plans, not just drink more water.
Source: www.weather.gov/safety/heat-wwIs it still called an excessive heat warning?
The National Weather Service heat safety page now uses Extreme Heat Warning and Extreme Heat Watch. You may still see Excessive Heat Warning in older articles and in some local coverage. They refer to the same tier of alert, and the action is the same either way.
Source: www.weather.gov/safety/heat-wwIs a fan enough during an extreme heat warning?
Not on its own in extreme heat. Once the air is hot enough, moving it around does not cool your body down. Go somewhere with air conditioning, such as a cooling center, a library, or a relative's house, and keep drinking water.
Source: www.weather.gov/safety/heat-wwHeat stroke is a medical emergency. Call 911.
Signs of heat stroke: throbbing headache, confusion, slurred speech, nausea, dizziness, body temperature above 103 degrees Fahrenheit, hot red dry or damp skin, rapid and strong pulse, fainting, loss of consciousness.
What to do: call 911 or get the person to a hospital immediately. Delay can be fatal. Move them somewhere cooler and bring their temperature down with cool cloths or a cool bath. Do not give them fluids.
Signs of heat exhaustion, which comes first: heavy sweating, weakness or tiredness, cool pale clammy skin, fast weak pulse, muscle cramps, dizziness, nausea or vomiting, headache, fainting.
What to do: move the person to a cooler place, preferably a well air conditioned room. Loosen clothing. Apply cool wet cloths or have them sit in a cool bath. Offer sips of water. Get medical help right away if the symptoms get worse or last longer than an hour.
Source: www.weather.gov/safety/heat-illnessHow a heat alert reaches you
Heat alerts are not on the National Weather Service list of alerts sent to cell phones as Wireless Emergency Alerts. Your phone will not buzz for an extreme heat warning.
Heat is the hazard people are least likely to hear about and most likely to underestimate. Check the forecast during a hot stretch instead of waiting to be told.
Source: www.weather.gov/wrn/weaWhere heat alerts are broadcast
NOAA Weather Radio All Hazards broadcasts official Weather Service warnings, watches, forecasts and other hazard information 24 hours a day, 7 days a week, directly from the nearest National Weather Service office.
It carries heat watches, warnings, and advisories along with everything else.
Source: www.weather.gov/nwr