Apparent Temperature Calculator
Work out the apparent ("feels like") temperature from air temperature, humidity and wind with the Steadman formula used by the Australian Bureau of Meteorology — in the shade or in the sun.
How it works
Shade: AT = Tₐ + 0.33 e − 0.70 ws − 4.00 · Sun: AT = Tₐ + 0.348 e − 0.70 ws + 0.70 Q ÷ (ws + 10) − 4.25 · e = (RH ÷ 100) × 6.105 × exp(17.27 Tₐ ÷ (237.7 + Tₐ)) hPa · Tₐ in °C, ws = wind at 10 m in m/s, Q = net radiation absorbed per m² of body surface (W/m²)
The apparent temperature of R. G. Steadman (1994) is the temperature at which a typical person would feel the same thermal stress in a reference environment. Unlike the heat index or wind chill, one formula covers the whole range: humidity (through the vapour pressure e) makes it feel warmer and wind makes it feel cooler. The Australian Bureau of Meteorology uses the shade version for its "feels like" figures; the radiation version adds the warming of direct sunshine.
Worked example
At 25 °C, 50% relative humidity and a 10 km/h wind (2.78 m/s) in the shade: e = 0.5 × 6.105 × exp(17.27 × 25 ÷ 262.7) = 15.8 hPa, so AT = 25 + 0.33 × 15.8 − 0.70 × 2.78 − 4.00 = 24.3 °C — it feels about 0.7 °C cooler than the air.
Sources: Australian Bureau of Meteorology — Thermal comfort observations (apparent temperature) · Steadman, R. G. (1994) Norms of apparent temperature in Australia, Aust. Met. Mag. 43, 1–16
Frequently asked questions
What does "feels like" temperature mean?
It is the temperature your body perceives once humidity, wind and sometimes sunshine are taken into account. Weather services compute it with formulas such as Steadman’s apparent temperature, the heat index or wind chill.
Is apparent temperature the same as the heat index?
Not exactly. The US heat index applies only in warm, humid conditions and ignores wind. Steadman’s apparent temperature works at any temperature and includes the cooling effect of wind.
Which wind speed should I use?
The formula expects the wind measured at the standard 10 m height, which is what weather stations and forecasts report.
How much does sunshine add?
With 300 W/m² of absorbed radiation and a light wind, direct sun can add 5–10 °C to the shade value — which is why standing in the sun on a summer day feels so much hotter.
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This calculator is for educational purposes. Double-check important results before acting on them.