Heat Index Converter
Calculate "feels like" temperature based on air temperature and humidity
Air Temperature
Relative Humidity (%)
Heat Index Results
Actual Temperature:
85.0 °F
Feels Like (Heat Index):
92.7 °F
Extreme Caution
Heat cramps and heat exhaustion possible with prolonged exposure.
Understanding Heat Index
Heat index is how hot it actually feels when humidity is combined with air temperature. High humidity prevents sweat from evaporating quickly, reducing the body's ability to cool itself.
The heat index formula is most accurate for temperatures above 80°F (27°C) and relative humidity above 40%.
Heat Index Effect
Hot Weather Safety Tips
- Stay hydrated by drinking plenty of fluids
- Avoid outdoor activities during peak heat (10am-4pm)
- Wear lightweight, light-colored, loose-fitting clothing
- Take frequent breaks in shaded or air-conditioned areas
- Check on vulnerable individuals (elderly, children, pets)
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About the Heat Index Converter
Calculate "feels like" temperature based on air temperature and humidity All conversions run instantly in your browser and nothing you enter is sent to a server.
Common Conversion Formulas
| From | To | Formula |
|---|---|---|
| Heat Index (°F) | Temperature (T in °F), Relative Humidity (RH%) | HI = -42.379 + 2.04901523×T + 10.14333127×RH - 0.22475541×T×RH - 0.00683783×T² - 0.05481717×RH² + 0.00122874×T²×RH + 0.00085282×T×RH² - 0.00000199×T²×RH² |
| Simple Heat Index (°F) | Temperature (T in °F), Relative Humidity (RH%) | HI ≈ 0.5 × [T + 61.0 + ((T-68.0)×1.2) + (RH×0.094)] |
| Heat Index (°C) | Heat Index (HI in °F) | HI(°C) = (HI(°F) - 32) × 5/9 |
| Health Risk | Heat Index (HI in °F) | 80-90°F: Caution, 90-105°F: Extreme Caution, 105-130°F: Danger, >130°F: Extreme Danger |