Heat Index Calculator

Heat index, also known as apparent temperature or humiture, is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. This is important because high humidity reduces the effectiveness of sweating to cool the body by reducing the rate of evaporation of moisture from the skin.

The heat index was developed by Robert G. Steadman in 1979 and is calculated using a complex formula that takes into account:

• Air temperature
• Relative humidity or dew point
• Human physiology and clothing

When the heat index is high:

• Stay hydrated by drinking plenty of fluids
• Avoid strenuous activities
• Stay in air-conditioned environments when possible
• Wear lightweight, light-colored clothing
• Check on elderly neighbors and those without air conditioning
• Never leave children or pets in cars

Note: The heat index values are for shaded locations only. Exposure to full sunshine can increase heat index values by up to 15°F.