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Heat Index Calculator (Feels-Like Temperature)

See how hot it really feels when humidity is high, or how cold with the wind, with the dew point and what the heat means for your health.

Rules last checked 25 October 2026Every step shown1 source

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%
km/h

Only used for wind chill, below 10 °C (50 °F).

Feels like

48.6 °C

Air temperature
38 °C
Dew point
25.8 °C
Worked out with
Heat index (US National Weather Service)
What it means
Danger: heat exhaustion is likely and heat stroke is possible with activity.

38 °C at 50% humidity feels like 48.6 °C. Danger: heat exhaustion is likely and heat stroke is possible with activity.

How it's worked out

  1. In °F and °C100.4 °F = 38 °C50% humidity
  2. Heat index (US National Weather Service)Rothfusz regression on °F and humidity48.6 °C
  3. Dew pointMagnus formula25.8 °C
  • The heat index is for shade with a light breeze. Full sun can add up to about 8 °C (15 °F). Drink water often, rest in the shade, and check on older people and children in a heatwave.

How it is worked out

From 27 °C (80 °F) up, the calculator uses the US National Weather Service heat index, a regression on temperature and humidity. At 10 °C (50 °F) and below, with wind above 4.8 km/h, it uses the wind chill formula shared by Environment Canada and the NWS. In between, the feels-like temperature is the air temperature.

Wind chill = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965TV^0.16 (°C, km/h)

Heat index risk levels

27 to 32 °C: caution · 32 to 39 °C: extreme caution · 39 to 51 °C: danger · above 51 °C: extreme danger.

In a heatwave, drink water often, stay in the shade during the hottest hours, and check on older people, children and anyone working outdoors.

Questions people ask

What is the heat index?

How hot it feels when humidity is added to the air temperature. Humid air slows sweat from evaporating, so the body cools less well.

What does 38 °C feel like at 50% humidity?

About 48.6 °C, in the danger range, where heat exhaustion is likely and heat stroke is possible with activity.

What is wind chill?

How cold it feels on exposed skin when wind carries heat away. At −10 °C with a 20 km/h wind, it feels like −17.9 °C.

What is the dew point?

The temperature at which the air would be saturated and dew would form. A dew point above about 20 °C feels muggy; at 30 °C and 50% humidity it is 18.4 °C.

Formula and rules last checked 25 October 2026Written and tested by the CalculatorDex teamReport a problem

Sources: US National Weather Service: The Heat Index Equation