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Glossary Science & Engineering

Heat index

The heat index is the "feels like" temperature that combines air temperature and relative humidity to show how hot it seems to the body.

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In more detail

At 90 °F and 70% humidity it feels like about 106 °F. The standard regression is valid only from 80 °F and 40% humidity, and full sun can add up to 15 °F.

Try these tools

Heat Index Calculator

Calculate the heat index — the "feels like" temperature from air temperature and relative humidity — using the NWS Rothfusz regression.

See also

  • Glossary Dew point
    The dew point is the temperature to which air must cool for water vapour to condense into dew; the higher it is, the muggier the air feels.
  • Glossary Wind chill
    Wind chill is the "feels like" temperature that shows how cold exposed skin feels when wind carries heat away.
  • Cheat sheet Weather Formulas Cheat Sheet
    The heat index, wind chill and dew point formulas with their valid ranges, plus °C/°F conversion.
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