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 under different humidity conditions.

2. How Does the Calculator Work?

The calculator uses the Rothfusz regression formula:

Where:

• \( HI \) — Heat index (perceived temperature in °F)
• \( T \) — Air temperature (°F)
• \( R \) — Relative humidity (%)
• \( c_1 \) to \( c_9 \) — Empirical coefficients

Explanation: The formula is a polynomial regression that models how humidity affects the body's perception of temperature.

3. Importance of Heat Index

Details: High heat index values indicate dangerous conditions where the body's ability to cool itself through sweating is impaired.

4. Using the Calculator

Tips: Enter the air temperature (°F) between -40°F and 140°F and relative humidity (%) between 0% and 100%.

5. Frequently Asked Questions (FAQ)

Q1: Why does humidity affect how hot it feels?
A: High humidity reduces sweat evaporation, which is the body's primary cooling mechanism, making it feel hotter than the actual temperature.

Q2: What's considered a dangerous heat index?
A: Heat index values above 90°F are considered cautionary, above 103°F dangerous, and above 125°F extremely dangerous.

Q3: Does this formula work for Celsius?
A: No, this is the Fahrenheit version. For Celsius, different coefficients and adjustments are needed.

Q4: Why are there adjustments to the formula?
A: The adjustments account for edge cases where the original polynomial doesn't model human perception as accurately.

Q5: What are the limitations of heat index?
A: It doesn't account for wind speed, solar radiation, or individual factors like clothing and physical activity.