Heat Index Calculator

Heat Index Equation:

\[ HI = -42.379 + 2.04901523 \times T + 10.14333127 \times RH - 0.22475541 \times T \times RH - 6.83783 \times 10^{-3} \times T^2 - 5.481717 \times 10^{-2} \times RH^2 + 1.22874 \times 10^{-3} \times T^2 \times RH + 8.5282 \times 10^{-4} \times T \times RH^2 - 1.99 \times 10^{-6} \times T^2 \times RH^2 \]

Heat Index (HI):

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1. What is the Heat Index Equation?

The Heat Index (HI) equation estimates the perceived temperature by combining air temperature and relative humidity. It indicates how hot it feels to the human body when moisture is considered, providing a more accurate measure of heat stress than temperature alone.

2. How Does the Calculator Work?

The calculator uses the Heat Index equation:

Where:

\( T \) — Temperature in degrees Fahrenheit (°F)
\( RH \) — Relative Humidity in percentage (%)

Explanation: The equation models the combined effect of temperature and humidity on the human body's perception of heat, with higher values indicating greater heat stress.

3. Importance of Heat Index Calculation

Details: Accurate Heat Index estimation is crucial for assessing heat-related health risks, planning outdoor activities, and issuing heat advisories to prevent heat exhaustion or heatstroke.

4. Using the Calculator

Tips: Enter temperature in °F and relative humidity in %. Valid inputs require temperature ≥80°F and humidity ≥40% for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: Why is Heat Index important?
A: It helps quantify the risk of heat-related illnesses by accounting for both temperature and humidity, which affect how the body cools itself through sweating.

Q2: What are the Heat Index risk categories?
A: Generally, 80-90°F: caution; 90-103°F: extreme caution; 103-124°F: danger; above 125°F: extreme danger.

Q3: When is Heat Index most relevant?
A: During hot and humid conditions, typically in summer months, especially for outdoor workers, athletes, and vulnerable populations.

Q4: Are there limitations to this equation?
A: It assumes shade and light wind conditions. Direct sunlight can increase the perceived temperature by up to 15°F.

Q5: Can Heat Index be used for Celsius inputs?
A: The standard equation requires Fahrenheit inputs. Convert Celsius to Fahrenheit first using: °F = (°C × 9/5) + 32.