Weather Calculators
Heat Index Calculator
Calculate heat index from temperature and humidity; view danger levels.
What is the Heat Index Calculator & How does it work?
The Heat Index Calculator determines the apparent temperature, which reflects how hot it feels when relative humidity is factored in. This is crucial for assessing heat-related health risks.The formula adjusts the air temperature to account for moisture levels, providing a more accurate measure of discomfort. Understanding heat index helps in planning outdoor activities and staying safe during hot weather.
HI = -42.379 + 2.04901523*T + 10.14333127*RH – 0.22475541*T*RH – 6.83783*T^2 – 5.481717*RH^2 + 1.22874*T*RH^2 + 0.085282*RH*T^2 – 0.000536*T^2*RH^2
HI = Heat Index, T = Temperature (°F), RH = Relative Humidity (%)
Parameters
°C
%
Heat Index
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Heat Danger Category
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Frequently Asked Questions
What is the heat index?
The heat index is a measure that combines air temperature and relative humidity to determine how hot it actually feels.
How do I use this calculator?
Enter the current air temperature in Fahrenheit and relative humidity percentage to get the heat index.
Why is the heat index important?
It helps assess heat-related health risks and plan outdoor activities safely during hot weather.
What does HI stand for in the formula?
HI stands for Heat Index, which is the calculated value representing how hot it feels with humidity.
Can I use this calculator for Celsius?
No, this calculator uses Fahrenheit for temperature. Convert your temperature to Fahrenheit first.
What if my relative humidity is not exact?
Estimate the closest percentage or round to the nearest whole number for a reasonable calculation.
Does the heat index change with altitude?
Yes, higher altitudes can affect both temperature and humidity, impacting the heat index.
Results are for informational purposes only and do not constitute professional advice.