Live heat advisories and extreme heat warnings, with satellite surface temperatures.
Alerts: U.S. National Weather Service. HeatRisk: experimental NWS forecast of the risk of heat-related impacts over the next 7 days, including levels below official alert criteria. Surface temperature: NASA MODIS satellite, worldwide, daily, with gaps under clouds. Heat alerts cover the United States. This page does not replace official warnings. In extreme heat, drink water, stay cool and check on others.
What This Heat Advisory Map Shows
This page shows active heat alerts on a live map. The alerts come from the U.S. National Weather Service and refresh every 5 minutes. Each colored area is under an extreme heat warning, watch or heat advisory. The list next to the map groups the alerts by type and shows how many areas are affected. You can turn on a satellite layer from NASA that shows how hot the ground surface is around the world, including in Europe, South Asia, the Middle East and Australia.
What Is HeatRisk?
HeatRisk is an experimental forecast from the National Weather Service. It shows the risk of heat-related impacts for the next 7 days, from 0 (little to no risk) to 4 (extreme). It looks at how unusual the heat is for the time of year, how long it lasts, including hot nights, and whether it is hot enough to harm people. HeatRisk can show a risk before an official heat advisory is issued, so a yellow or orange area does not mean a warning is active. Use the day menu to move through the week.
Is There a Heat Advisory Near Me?
Press My location and allow location access. The map moves to your position, and a box above the map lists every active heat alert at your exact location. If the box says there are no alerts, nothing is active for your spot right now. Alerts are issued for the United States. For other countries, check your national weather service.
Watch, Advisory and Warning
- Heat advisory: Hot weather is expected and can be dangerous, especially for children, older adults and people who work outside.
- Extreme heat watch: Dangerous heat is possible in the next 1 to 3 days. Make plans.
- Extreme heat warning: Dangerous heat is happening or about to happen. The National Weather Service used to call this an excessive heat warning.
What Is the Heat Index?
The heat index is how hot it feels when you combine air temperature with humidity. Sweat cools you by evaporating, and high humidity slows that down. At 90°F (32°C) with 70 percent humidity, the heat index is about 106°F (41°C). The levels that trigger an alert vary by region, because people in Phoenix are used to heat that would be a crisis in Seattle. A heat advisory is often issued around a heat index of 100 to 105°F (38 to 41°C), and a warning at 105°F (41°C) or higher.
Why Heat Is So Dangerous
Heat is one of the deadliest weather hazards in the United States, with well over 100 deaths in an average year, and it kills quietly. Hot nights are a major risk, because the body cannot recover when the air stays warm after dark. Cities are hotter than the countryside because pavement and buildings hold heat. This is called the urban heat island effect.
Heat Waves in History
- Chicago, 1995: A heat wave killed 739 people in one week.
- Europe, 2003: An estimated 70,000 people died in the summer heat across the continent.
- Europe, 2022: About 61,000 heat-related deaths in one summer, according to a study in Nature Medicine.
- Pacific Northwest, 2021: A heat dome pushed Lytton, British Columbia, to 121.3°F (49.6°C), a Canadian record, and hundreds of people died in Canada and the U.S.
- Phoenix, 2023: 31 days in a row at 110°F (43°C) or higher.
- Mecca, 2024: More than 1,300 pilgrims died in the heat during the Hajj.
- Death Valley, 1913: 134°F (56.7°C), the hottest air temperature ever reliably recorded on Earth.
Heat Exhaustion and Heat Stroke
Heat exhaustion causes heavy sweating, weakness, dizziness, headache and nausea. Move to a cool place, drink water and rest. Heat stroke is an emergency. Signs are a body temperature of 103°F (39.4°C) or higher, hot dry skin or confusion, fainting or seizures. Call emergency services right away and cool the person down while you wait.
How to Stay Safe
Drink water before you feel thirsty, and avoid alcohol and sugary drinks. Stay in air conditioning if you can, and take breaks from outdoor work in the shade. Wear light, loose clothes. Check on older neighbors and people who live alone. Never leave a child or a pet in a parked car. The temperature inside a car can rise almost 20°F (11°C) in just 10 minutes. EarthInformer is an information site and does not issue official warnings.
Source: Alerts from the U.S. National Weather Service. Surface temperature from NASA MODIS.
Heat Advisory FAQ
Press My location on the map above. It shows every active heat alert at your position in the United States.
An advisory means hot weather can be dangerous, especially for children, older adults and outdoor workers. A warning means dangerous heat is happening or about to happen, so take action right away.
It depends on the region. In many places, an advisory is issued around a heat index of 100 to 105°F (38 to 41°C), and a warning at 105°F (41°C) or higher.
The heat index is how hot it feels when air temperature is combined with humidity. High humidity slows sweat from evaporating, so the body cools less.
Heat exhaustion causes heavy sweating, weakness and nausea, and it can be treated by cooling down and drinking water. Heat stroke is an emergency with a body temperature of 103°F (39.4°C) or higher and confusion. Call emergency services.
The body needs cooler air at night to recover from the day’s heat. When it stays warm after dark, the risk of heat illness goes up, especially for older people and in cities.
The hottest air temperature ever reliably recorded is 134°F (56.7°C), in Death Valley, California, in July 1913.