The heat index provides information about how hot it feels
outside in the shade. It is a measure of the air temperature in relation to the
relative humidity for a particular day.
The National Weather
Service lists a heat index each day in the newspaper to alert people of the
risk for a heat-related illness. Direct exposure to the sun can increase the
risk for a heat-related illness on days when the heat index is high. Babies, older adults, or anyone with a health condition may have more risk of problems with the heat because of their age and general health.
A heat index of:
80°F (27°C) to
89°F (32°C) may cause
90°F (32°C) to 104°F (40°C) may
cause heat cramps or heat exhaustion.
105°F (41°C) to
129°F (54°C) may cause
heat cramps or heat exhaustion, and heatstroke is
130°F (54°C) or higher may cause heatstroke.
Prevention measures during days of high heat index will
help reduce the risk of a heat-related illness. When the outdoor humidity is
greater than 75%, losing body heat by sweating is not as effective, so other
measures to keep cool are needed.
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine
The Health Encyclopedia contains general health information. Not all treatments or services described are covered benefits for Kaiser Permanente members or offered as services by Kaiser Permanente. For a list of covered benefits, please refer to your Evidence of Coverage or Summary Plan Description. For recommended treatments, please consult with your health care provider.