🌡️ Heat Index Calculator

Overview

The Heat Index Calculator helps determine how hot the weather actually feels to the human body by combining air temperature and relative humidity. When humidity is high, sweat evaporates more slowly, making it feel hotter than the actual air temperature. This calculator uses a scientifically accepted formula to provide accurate “feels-like” temperature values.

What Is Heat Index?

The Heat Index, also known as the apparent temperature, represents how hot it feels when air temperature and humidity are considered together. It is widely used by meteorological agencies to assess heat-related health risks.

Formula Used

This calculator uses the NOAA Heat Index (Rothfusz Regression) formula, which is the standard method adopted by weather services worldwide.

How to Use the Heat Index Calculator

Enter the air temperature in degrees Fahrenheit (°F).
Enter the relative humidity as a percentage (%).
Click Calculate.
The heat index value and associated risk level are displayed instantly.

Example Calculation

Inputs:

Air Temperature: 90 °F
Relative Humidity: 60%

Output:

Heat Index: 99.68 °F
Risk Level: Heat exhaustion possible

Why This Calculator Is Useful

Helps understand real-feel temperature
Assists in identifying heat stress risks
Useful for outdoor planning and safety
Ideal for students, workers, athletes, and the general public

Heat Index Risk Levels (General Guide)

Below 90°F: Little to no risk
90–103°F: Heat exhaustion possible
103–124°F: Heat cramps and exhaustion likely
125°F and above: Heat stroke highly likely

Who Can Use This Tool

General public monitoring hot weather
Outdoor workers and athletes
Health and safety professionals
Students and educators
Event planners and travelers

Accuracy & Reliability

The calculator uses validated meteorological formulas and includes input validation to ensure realistic and accurate results. Values are rounded to two decimal places for clarity while maintaining precision.

Common Applications

Weather awareness and safety planning
Outdoor work and sports preparation
Heat stress education
Health risk assessment during heat waves

Safety Note

The heat index is a guideline and does not replace medical advice. During extreme heat, always stay hydrated, avoid prolonged sun exposure, and seek medical help if heat-related symptoms occur.