Physics and Engineering
Heat Index Calculator
Heat Index Calculator calculate the U.S. National Weather Service heat-index estimate from air temperature and relative humidity with domain checks.
Physics and Engineering
Heat Index Calculator
Calculate the U.S. National Weather Service heat-index estimate from air temperature and relative humidity with domain checks.
Formula
Heat index uses the Rothfusz regression in degrees Fahrenheit with low- and high-humidity adjustments where applicable.
About the Heat Index Calculator
Calculate the U.S. National Weather Service heat-index estimate from air temperature and relative humidity with domain checks.
How the Heat Index Calculator Works
The simple expression is averaged with air temperature to determine whether the full polynomial regression applies, then official humidity adjustments are evaluated before unit conversion.
Formula
Heat index uses the Rothfusz regression in degrees Fahrenheit with low- and high-humidity adjustments where applicable.
The calculation runs in your browser. Values are validated for required ranges, compatible units, and method-specific restrictions before results are displayed.
Required Inputs
- Air temperature (required) - enter in F.
- Relative humidity (required) - enter in %.
Results Reported
The result panel reports the final answer and the intermediate quantities needed to check the calculation:
- Heat index (F)
- Heat index (C)
- Heat-index minus air temperature (F)
- Formula mode
Heat Index Calculator Example
Select Example Data in the calculator to load this reproducible input set:
| Input | Example value |
|---|---|
| Air temperature | 95 F |
| Relative humidity | 55 % |
How to Use the Calculator
- Confirm that the calculator title and formula match the quantity you need.
- Enter every required value using the unit shown with its field.
- Select Example Data to inspect a valid input set, or enter your own values and select Calculate.
- Review all reported values and the displayed formula before using the answer.
- Use Copy Result or Download CSV when you need a reusable record.
Accuracy and Limitations
The formula is intended for shaded, light-wind conditions and is generally meaningful for warm humid weather. Direct sun, wind, clothing, health, and exertion alter heat stress.
Keep units consistent, use measurements that represent the actual situation, retain full precision during the calculation, and round only the final answer. Professional decisions may require current official rules, field measurements, laboratory methods, or specialist review.
Frequently Asked Questions
What does the Heat Index Calculator calculate?
Calculate the U.S. National Weather Service heat-index estimate from air temperature and relative humidity with domain checks.
Which formula does the Heat Index Calculator use?
Heat index uses the Rothfusz regression in degrees Fahrenheit with low- and high-humidity adjustments where applicable. The simple expression is averaged with air temperature to determine whether the full polynomial regression applies, then official humidity adjustments are evaluated before unit conversion.
What should I check before using the Heat Index Calculator result?
The formula is intended for shaded, light-wind conditions and is generally meaningful for warm humid weather. Direct sun, wind, clothing, health, and exertion alter heat stress.