1. What is Heat Index?

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

Purpose: It helps people understand the apparent temperature and potential heat-related risks.

2. How is Heat Index Calculated?

The calculator uses the Rothfusz regression formula:

Where:

• \( HI \) — Heat Index (°F)
• \( T \) — Temperature (°F)
• \( RH \) — Relative Humidity (%)

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

3. Importance of Heat Index

Details: High heat index values indicate increased risk of heat-related illnesses. It's used by weather services and health organizations to issue heat advisories.

4. Using the Calculator

Tips: Enter the temperature in °F and relative humidity in %. The calculator will show the apparent temperature (heat index).

5. Frequently Asked Questions (FAQ)

Q1: Why does humidity make it feel hotter?
A: High humidity reduces the body's ability to cool itself through sweat evaporation, making the temperature feel hotter than it actually is.

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

Q3: Does this work for temperatures below 80°F?
A: The formula is only accurate for T ≥ 80°F and RH ≥ 40%. Below these values, heat index equals the actual temperature.

Q4: How is heat index different from "feels like" temperature?
A: Heat index specifically accounts for humidity's effect on human perception of temperature, while "feels like" may include wind chill factors.

Q5: Are there different formulas for different countries?
A: Yes, some countries use similar indices like Canada's Humidex or Australia's Apparent Temperature, which may use slightly different formulas.