Heat Index Calculator
Heat Index Calculator Online – Calculate Heat Index Easily
Intro
A Heat Index Calculator online is a practical tool that helps you determine how hot it actually feels when humidity is combined with air temperature. While a thermometer shows the air temperature, the heat index reflects the “feels-like” temperature, which is crucial for health, comfort, and safety.
This tool is especially useful for outdoor workers, athletes, farmers, parents, and anyone exposed to hot weather. Instead of guessing, you can instantly calculate the heat index and take precautions against heat-related illnesses such as dehydration, heat exhaustion, and heat stroke.
Formula / Working
The Heat Index (HI) is calculated using a complex formula that combines air temperature (T) and relative humidity (RH). For temperatures above 27°C (80°F) and humidity above 40%, the formula is: HI=−42.379+2.04901523T+10.14333127RH−0.22475541TRH−6.83783×10−3T2−5.481717×10−2RH2+1.22874×10−3T2RH+8.5282×10−4TRH2−1.99×10−6T2RH2HI = -42.379 + 2.04901523T + 10.14333127RH – 0.22475541TRH – 6.83783 \times 10^{-3}T^2 – 5.481717 \times 10^{-2}RH^2 + 1.22874 \times 10^{-3}T^2RH + 8.5282 \times 10^{-4}TRH^2 – 1.99 \times 10^{-6}T^2RH^2HI=−42.379+2.04901523T+10.14333127RH−0.22475541TRH−6.83783×10−3T2−5.481717×10−2RH2+1.22874×10−3T2RH+8.5282×10−4TRH2−1.99×10−6T2RH2
Where:
- HI = Heat Index (°F)
- T = Air Temperature (°F)
- RH = Relative Humidity (%)
The calculator automatically applies this formula to provide the heat index in Fahrenheit or Celsius.
Step-by-Step Usage
Here’s how to use the Heat Index Calculator online:
- Enter the air temperature (°C or °F).
- Enter the relative humidity (%).
- Click “Calculate.”
- Instantly view the heat index (feels-like temperature).
Examples
Example 1: Typical Summer Day
- Temperature = 90°F (32°C)
- Humidity = 60%
Result: The heat index is around 100°F (37.8°C), which feels much hotter than the actual air temperature.
Example 2: Hot and Humid
- Temperature = 95°F (35°C)
- Humidity = 70%
Result: The heat index rises to 124°F (51°C), which is dangerous for prolonged outdoor activities.
Example 3: Warm but Dry
- Temperature = 85°F (29°C)
- Humidity = 30%
Result: The heat index is 83°F (28°C), which feels slightly cooler due to lower humidity.
FAQs
1. What is a heat index calculator?
It’s an online tool that calculates the “feels-like” temperature based on air temperature and humidity.
2. Why is the heat index important?
It helps people understand the risks of heat-related illnesses during hot and humid conditions.
3. Can it be used in both Celsius and Fahrenheit?
Yes, the calculator supports both measurement units.
4. Is the heat index the same as humidity?
No. Humidity is the amount of water vapor in the air, while heat index combines humidity and temperature to show how hot it feels.
5. Who should use this calculator?
Outdoor workers, athletes, parents, health professionals, and anyone who wants to stay safe in hot weather.