Heat Index Calculator
Calculate the perceived temperature based on humidity and air temperature
Heat Index Calculator
This calculator estimates the temperature felt by the body as a result of air temperature and relative humidity. Heat index is often referred to as humiture, and measures the perceived rather than the actual temperature.
Quick Navigation
💧 Use Relative Humidity
📊 Result
Note: The heat index is calculated for shaded areas with light wind. Exposure to full sunshine can increase heat index values by up to 14°F (8°C).
🌊 Use Dew Point Temperature
Result
Relative Humidity: 62%
📚 Understanding Heat Index
What is Heat Index?
Heat index is often referred to as humiture, and is similar to wind chill in its attempt to measure the perceived rather than the actual temperature. For example, an air temperature of 83°F with a relative humidity of 70% would result in an estimated 88°F perceived temperature. This difference in perceived and actual temperature is the result of a mixture of air temperature, relative humidity, and wind speed.
The perception of heat is subjective, and can be affected by various factors such as menopause, pregnancy, and the effects of drugs or withdrawal, as well as differences in hydration, body shape, and metabolism. A higher relative humidity affects normal body cooling by reducing the rate of evaporation of sweat.
How to Calculate Heat Index?
Like the Wind Chill Temperature Index, the heat index used by the National Weather Service (NWS) in the United States is based on many assumptions such as body mass, height, clothing, individual physical activity, blood thickness, and wind speed. The equation was developed by George Winterling in 1978, and is meant to be valid for temperatures of 80°F or higher, and relative humidity of 40% or more.
Effects of Heat Index
| Celsius | Fahrenheit | Notes |
|---|---|---|
| 27-32°C | 80-90°F | Caution: fatigue is possible with prolonged exposure and activity. Continuing activity could result in heat cramps. |
| 32-41°C | 90-105°F | Extreme caution: heat cramps and heat exhaustion are possible. Continuing activity could result in heat stroke. |
| 41-54°C | 105-130°F | Danger: heat cramps and heat exhaustion are likely; heat stroke is probable with continued activity. |
| Over 54°C | Over 130°F | Extreme danger: heat stroke is imminent. |
Note: Exposure to full sunshine can increase heat index values by up to 14°F. Heat index values are particularly important for children. Young children are generally in more danger due to factors including larger skin surface relative to their small bodies, higher heat production as a result of exercise, and typically sweating less than adults.
Important Safety Information
Thirst is a late sign of dehydration, and it is important to remain hydrated, particularly before, during, and after outdoor activities, especially those involving heavy physical exertion.
In addition to children, people with certain conditions, including obesity, diabetes, heart disease, cystic fibrosis, and mental retardation are at greater risk of overheating and dehydration.