Heat index
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.
A heat index of:
- 80F to 89F can cause fatigue.
- 90F to 104F can cause heat cramps or heat exhaustion.
- 105F to 129F is likely to cause heat cramps or heat exhaustion, and heatstroke is possible.
- 130F or higher is likely to 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.
| Author | Jeannette Curtis |
| Author | Caroline Rea, RN, BS, MS |
| Editor | Kathleen M. Ariss, MS |
| Editor | Susan Van Houten, RN, BSN, MBA |
| Associate Editor | Tracy Landauer |
| Associate Editor | Pat Truman, MATC |
| Primary Medical Reviewer | Patrice Burgess, MD - Family Medicine |
| Primary Medical Reviewer | Adam Husney, MD - Family Medicine |
| Primary Medical Reviewer | Kathleen Romito, MD - Family Medicine |
| Last Updated | May 25, 2007 |
WebMD Medical Reference from Healthwise