Heat Index Calculator
Instantly calculate the heat index, often called the 'feels-like' or apparent temperature, with our free online Heat Index Calculator. Understand the real-world heat risk by factoring in air temperature and humidity.
How to Use Our Heat Index Calculator
Follow these simple steps to accurately determine the apparent temperature with our free heat index tool.
Our Heat Index Calculator Features
Discover the advantages of using our free and accurate heat index calculator for your weather safety needs.
NWS Formula Accuracy
Our heat index calculator utilizes the official U.S. National Weather Service (NWS) formula for the most reliable apparent temperature results.
Instant Heat Risk Levels
Immediately understand the danger level, from safe to extreme danger, based on the calculated heat index.
Dual Unit Support (C/F)
Seamlessly switch between Celsius and Fahrenheit to calculate the heat index in the units you prefer.
Dew Point Calculation Option
Offers an alternative calculation method using dew point for greater flexibility and accuracy in your weather analysis.
Mobile-Friendly Design
Use our heat index calculator on any device, whether you're at your desk or on the go, thanks to a responsive interface.
Free and Unlimited Use
This weather tool is completely free to use with no limitations. Perform as many heat index calculations as you need.
Heat Index Calculator FAQ
Find answers to common questions about the heat index, apparent temperature, and how to use our calculator.
What is the Heat Index?
The heat index, or apparent temperature, is a measure that combines air temperature and relative humidity to determine how hot it actually feels to the human body. Our calculator provides this 'feels-like' temperature.
How Accurate Is This Heat Index Calculator?
This calculator uses the official, widely-accepted formula from the U.S. National Weather Service (NWS), ensuring a high degree of accuracy for your heat index estimations.
Why is the Heat Index Important for Safety?
The heat index is a crucial weather metric for safety. High heat index values can lead to heat-related illnesses like heat exhaustion and heatstroke. Knowing the apparent temperature helps you take necessary precautions.
What's the Difference Between Humidity and Dew Point?
Relative humidity is the percentage of water vapor in the air relative to the maximum it can hold at that temperature. Dew point is the temperature at which air becomes saturated. Our calculator can use either for determining the heat index.
Does Wind Affect the Heat Index?
The standard heat index formula does not account for wind. Wind typically helps cool the body, so the 'feels-like' temperature might be lower than what the heat index calculator shows on a windy day. The opposite is true for the wind chill factor in winter.
Is This Calculator a Heat Index Chart?
In a way, yes. While the National Weather Service provides static heat index charts, our calculator is an interactive and more user-friendly version that instantly computes the specific apparent temperature for your inputs.