Extreme Heat

Heat Waves


A heat wave is a long time of extreme heat. It is often with high humidity. These conditions can be dangerous and even life-threatening for people who don’t do what they ought to do to keep themselves safe.

Heat can kill people because it pushes the human body past what it can handle. In extreme heat and high humidity, water evaporation is slowed and the body must work extra hard to keep a normal temperature.
Extreme Heat
Most heat problems occur because the person has been overexposed to heat or has over-exercised for his or her age and physical condition. Older adults, young children and those who are sick or overweight are more likely to give in to extreme heat.

The National Weather Service does not offer a direct definition of a heat wave but it is generally accepted as describing a period of three or more days where temperatures reach 90 degrees Fahrenheit or higher. It can however, be described as any event lasting three or more days where temperatures are 10 degrees hotter than the normal temperatures. 


Heat waves can pose serious threats to life. The National Weather Service began issuing products to help with heat warnings for the general public. 

Heat Warning System


The National Weather Service issues excessive heat outlooks, watches, warnings and advisories to provide advanced notice of excessive heat events for the protection of life and property.

Excessive Heat Outlooks/Advisories


Issued when the potential exists for an excessive heat event in the next 3-7 days. An Outlook provides information to those who need considerable lead time to prepare for the event such as public utility staff, emergency managers and public health officials.Heat Index values are forecast to meet locally defined advisory criteria for one to two days (daytime highs=100-105° Fahrenheit).

Excessive Heat Watches


Issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. A Watch is used when the risk of a heat wave has increased but its occurrence and timing is still uncertain. There is a good chance for an excessive heat event to meet or exceed local Excessive Heat Warning criteria in the next 24 to 72 hours

A Watch provides enough lead time so that those who need to prepare can do so, such as cities officials who have excessive heat event mitigation plans.

Excessive Heat Warning


Issued when an excessive heat event is expected in the next 36 hours. These products are issued when an excessive heat event is occurring, imminent or has a very high probability of occurring. Heat Index values are forecast to meet or exceed locally defined warning criteria for at least two days (daytime highs=105-110° Fahrenheit).

The warning is used for conditions posing a threat to life. An advisory is for less serious conditions that cause significant discomfort or inconvenience and, if caution is not taken, could lead to a threat to life.

This information was provided by the National Weather Service.

Extreme Heat Safety

  1. Before
  2. During
  3. After
  4. Know The Terms

Before Extreme Heat



Ways to get ready for long periods of heat:

  • You should make an emergency kit and family communications plan.
  • Put in window air conditioners snugly; insulate if needed.
  • Check air-conditioning ducts for proper insulation.
  • Put in short-term window reflectors for use between windows and drapes, such as aluminum foil-covered cardboard, to reflect heat back outside.
  • Weather-strip doors and sills to keep cool air in.
  • Cover windows that receive morning or afternoon sun with drapes, shades, awnings or louvers. Outdoor awnings or louvers can lower the heat that comes in a home by up to 80 percent.
  • Keep storm windows up all year.
  • Listen to local weather forecasts. Stay alert about upcoming temperature changes.
  • Know those in your neighborhood who are elderly, young, sick or overweight. They are more likely to be harmed by excessive heat and may need help.
  • People living in cities may be at more risk from the long periods of heat than people living in rural areas.
  • Get trained in first aid to learn how to treat heat-related emergencies.