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Heat advisory in the United States

Extreme heat can be dangerous or even life-threatening for people, especially the elderly, people with chronic illnesses, the young (under age four) and those who are overweight. It is the number one weather-related killer. On average, more than 1,500 people in the U.S. die each year from excessive heat. Common-sense preparations can save lives.

Heat wave terms

  • Heat Index or “Apparent Temperature” – An estimate of the temperature that the body feels when the effects of heat and humidity are combined. Note that exposure to direct sunlight can increase the heat index by as much as 15° Fahrenheit.
  • Excessive Heat Outlook – A heat wave may develop in the next 3 to 7 days.
  • Excessive Heat Watch – Conditions are favorable for a heat wave (high Heat Index) in the next 12 to 48 hours.
  • Heat Advisory – An uncomfortable, potentially dangerous heat wave (daytime highs = 100-105° F) is forecast within the next 36 hours.
  • Excessive Heat Warning – A dangerous heat wave (daytime highs = 105-110° F) is forecast within the next 36 hours.

For more information on heat advisories, see: