Heat Index: Shade and light-wind heat index, not a complete heat-stress assessment.
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Heat Index Calculator for United States
US · 12,345.67US customary measurementsRoad distance: miles
United States display and unit preferences. The stated calculation method is used. Review the labeled units before entering your values.
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Your details
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Example only. Enter the amount or rate applicable to your situation in United States.
Heat index (°C)
40.409
United States · calculated from your inputs
Heat index (°F)104.737
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How this result was calculated
Use the NWS simple estimate in mild conditions and Rothfusz regression with low/high humidity adjustments when the preliminary index reaches 80°F.
Country setup: United States. Displayed measurements are converted to the formula's base units internally.
Assumption: Shade and light-wind heat index, not a complete heat-stress assessment. Source: https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml United States display and unit preferences. The stated calculation method is used. Review the labeled units before entering your values.
Calculation version 1.0.0 · Support state: generic
Formula and method
Use the NWS simple estimate in mild conditions and Rothfusz regression with low/high humidity adjustments when the preliminary index reaches 80°F.
This calculation uses the values you enter. It runs in your browser and does not request a location or account.
Worked example
The same air temperature can feel hotter at higher relative humidity.
Questions people ask
Which method does this tool use?
Use the NWS simple estimate in mild conditions and Rothfusz regression with low/high humidity adjustments when the preliminary index reaches 80°F.
What should I check before using the result?
Shade and light-wind heat index, not a complete heat-stress assessment. Source: https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml