Heat index
How hot does the air actually feel?
Heat index combines air temperature and relative humidity. Use the live forecast for timing, the calculator for a specific scenario, and the guide for the assumptions behind the number.
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Forecast, calculate or understand.
Heat index calculator
Enter temperature and humidity, inspect worked examples and use the embeddable chart.
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Heat index chart guide
Understand ranges, shaded light-wind assumptions and why direct sun changes the decision.
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Heat index vs. feels like
Learn when the labels match and why two weather providers can show different apparent temperatures.
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Heat index versus WBGT
Compare the inputs, scales and best use case for each heat measure.
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Heat acclimatization
Learn why gradual adaptation can reduce—but never eliminate—heat risk.
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City forecasts
Check today's heat index by location.
These curated pages combine location-specific forecast data with hourly planning context. Search results for other cities remain available without being added automatically to the index.