Heat Index Calculator
Calculate feels like temperature from heat and humidity.
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How It Works
Combines temperature and humidity to calculate apparent temperature using Rothfusz equation. High humidity prevents sweat evaporation making it feel hotter.
Formula
Rothfusz heat index equationQuick Reference
Common calculations — results you can verify instantly.
90°F, 80% humidity
Rothfusz equation
Feels like 99°F
95°F, 60% humidity
Rothfusz equation
Feels like 101°F
100°F, 90% humidity
Extreme danger
Feels like 132°F
Tips & Shortcuts
Above 40C heat index: dangerous. Above 54C: extreme danger.
Direct sunlight adds 8-15C to apparent temperature.
Common Mistakes
Only checking temperature without humidity
35C at 90% humidity feels like 55C.
Using same index for sunny and shaded
Direct sunlight adds 8-15C to apparent temperature.
Frequently Asked Questions
Above 40C danger. Above 51C extreme danger with heat stroke likely.
High humidity slows sweat evaporation reducing body cooling.
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