Heat Index Calculator

Heat Index Formula:

\[ HI = -42.379 + 2.04901523T + 10.14333127RH - 0.22475541T \times RH - 0.00683783T^2 - 0.05481717RH^2 + 0.00122874T^2 \times RH + 0.00085282T \times RH^2 - 0.00000199T^2 \times RH^2 \]

Heat Index:

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1. What is a Heat Index Calculator?

Definition: This calculator estimates the heat index (apparent temperature) based on air temperature and relative humidity using the NOAA formula.

Purpose: It helps assess how hot it feels when humidity is factored with the actual air temperature, important for health and safety.

2. How Does the Calculator Work?

The calculator uses the NOAA heat index formula:

\[ HI = -42.379 + 2.04901523T + 10.14333127RH - 0.22475541T \times RH - 0.00683783T^2 - 0.05481717RH^2 + 0.00122874T^2 \times RH + 0.00085282T \times RH^2 - 0.00000199T^2 \times RH^2 \]

Where:

\( HI \) — Heat index (apparent temperature in °F)
\( T \) — Air temperature (°F)
\( RH \) — Relative humidity (%)

Explanation: The formula accounts for how humidity affects the body's ability to cool itself through perspiration.

3. Importance of Heat Index

Details: The heat index helps prevent heat-related illnesses by indicating how hot it feels rather than just the actual temperature.

4. Using the Calculator

Tips: Enter the temperature in °F and relative humidity in %. Both values must be valid (humidity between 0-100%).

5. Frequently Asked Questions (FAQ)

Q1: Why is heat index important?
A: It indicates the perceived temperature that accounts for humidity's impact on human comfort and health risks.

Q2: What temperature range is valid for heat index?
A: The formula works best for temperatures above 80°F (27°C) and humidity above 40%.

Q3: What are the health risks at different heat index levels?
A: 80-90°F: Caution; 90-103°F: Extreme caution; 103-124°F: Danger; 125°F+: Extreme danger.

Q4: Can I use Celsius temperatures?
A: No, this formula requires Fahrenheit inputs. Convert Celsius to Fahrenheit first.

Q5: Why does high humidity make it feel hotter?
A: Humidity reduces sweat evaporation, impairing the body's natural cooling mechanism.