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Heat Index Calculator — NWS Feels-Like Temperature

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Temperature unit The NWS equations are evaluated in °F internally; Celsius inputs are converted first.Air temperature Enter the measured shade air temperature in the unit selected above.Relative humidity (%) Enter relative humidity from 0% to 100%.

Calculated result

37.1 °C / 98.7 °F

NWS method branch: NWS Rothfusz regression

Heat category screen: Extreme caution

Difference from air temperature: +9.1 °F (+5.1 °C)

No Rothfusz humidity adjustment applies.

Show the working

1. Convert/normalize air temperature: 32 °C = 89.6 °F; RH = 60%.
2. First NWS screen: 0.5 × [89.6 + 61 + (89.6 − 68) × 1.2 + 60 × 0.094] = 91.08 °F; average with air temperature = 90.34 °F.
3. Because the averaged screen is at least 80 °F, apply Rothfusz: HI = −42.379 + 2.04901523T + 10.14333127RH − 0.22475541TRH − 0.00683783T² − 0.05481717RH² + 0.00122874T²RH + 0.00085282TRH² − 0.00000199T²RH².
4. No Rothfusz humidity adjustment applies.
5. Final heat index = 98.73 °F = 37.07 °C.

NWS heat index assumes shade and light wind. Direct sunshine can make conditions feel substantially hotter; use official weather alerts and WBGT guidance when sun, exertion or occupational heat stress matters.

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