1. What is the Heat Index?

Definition: The Heat Index (HI) is a measure of how hot it feels when relative humidity is factored with the actual air temperature.

Purpose: It helps assess the risk of heat-related illnesses by indicating the perceived temperature to the human body.

2. How Does the Calculator Work?

The calculator uses the NOAA heat index formula:

Where:

• \( HI \) — Heat Index (°F)
• \( T \) — Temperature (°F)
• \( R \) — Relative Humidity (%)
• \( c_1 \) to \( c_9 \) — Empirical coefficients

Note: The formula is only valid when temperature is 80°F or higher and relative humidity is 40% or higher.

3. Importance of Heat Index

Details: The heat index is crucial for:

• Heat safety planning
• Outdoor activity guidelines
• Health risk assessment
• Weather forecasting

4. Using the Calculator

Tips: Enter the temperature in °F and relative humidity in %. Both values are required.

5. Frequently Asked Questions (FAQ)

Q1: Why does humidity affect how hot it feels?
A: High humidity reduces the body's ability to cool itself through sweat evaporation, making the temperature feel hotter.

Q2: What's considered a dangerous heat index?
A: Heat indices above 103°F are dangerous, and above 125°F is extremely dangerous with high risk of heat stroke.

Q3: Why is there a minimum temperature/humidity?
A: The formula was developed specifically for conditions where heat index becomes significant (≥80°F and ≥40% RH).

Q4: Can I use Celsius values?
A: No, the NOAA formula is specifically designed for Fahrenheit inputs. Convert Celsius to Fahrenheit first.

Q5: How accurate is the heat index calculation?
A: Very accurate for the specified range, but actual perception can vary based on individual factors and wind conditions.