Extreme heat, often referred to as a "heat wave", is an extended period of high temperature usually accompanied by high humidity. Extreme heat kills by pushing the human body beyond its limits. In extreme heat and high humidity, evaporation is slowed and the body must work extra hard to maintain a normal temperature. Older adults, young children, and those who are sick or overweight are more likely to be severely affected by extreme heat.

When authorities monitor extreme heat conditions the term "heat index" is used. This index measures the effects of heat and humidity. When heat and humidity combine to reduce the amount of evaporation of sweat from the body, outdoor exercise becomes dangerous even for those in good shape. In the District, the Heat Emergency Plan is activated when the heat index reaches 95 degrees.

To learn more, visit heat.dc.gov

For a list of the District's cooling centers, click here.