Extreme Heat

Extreme heat is a period of high heat and humidity with temperatures above 90 degrees for at least two to three days.

Heat Advisories

  • A heat advisory means that people can be affected by heat if precautions are not taken. The issuance of a heat advisory is important to raise public awareness that these precautions need to be taken. Heat advisories are also used to trigger other actions and regulations such as no evictions, no turning off power, changing outdoor work requirements, etc.

Excessive Heat Watches

  • Issued when Heat Warning criteria is possible (50-79%) 1 to 2 days in advance. 


  • Criteria for an Excessive Heat Warning is a heat index of 105 °F or greater that will last for 2 hours or more. A heat warning means that some people can be seriously affected by heat if precautions are not taken.
  • In addition to raising public awareness, the issuance of a heat warning will alert hospitals and officials to take certain actions to prepare and respond to an increase in emergency calls and activate programs to check on elderly and the home bound. In some cases, cooling centers can be open or designated and donation programs activated for fans and air conditioners. As in the case of an advisory, certain regulations may change such as turning off people's electricity, evictions, and outside work requirements.