Heat index calculator (feels-like temperature)
Find the feels-like heat by combining temperature and humidity — how hot it really feels.
The heat index combines temperature and humidity: the more humid, the less sweat evaporates and the hotter it feels. Valid for heat (above ~27°C).
How the calculation works
The heat index uses the Rothfusz equation, which weighs temperature and relative humidity. With high humidity, sweat evaporates less and the body cools poorly — so it "feels" hotter than the thermometer reads.
Examples
- 32 °C at 70% humidity: feels like ~41 °C (danger zone).
- 30 °C in dry air (30% humidity): feels close to the actual temperature.
Frequently asked questions
Is heat index the same as wind chill?
It is the feels-like for heat (temperature + humidity). In the cold, wind chill is what matters.
Why does humidity make heat worse?
The body cools by evaporating sweat. In humid air, sweat barely evaporates and cooling drops.
At what index should I worry?
Above ~41 °C there is real risk of exhaustion and heatstroke on prolonged effort. Hydrate and reduce activity.
At what heat index does it get dangerous?
From 32 to 41 °C cramps and exhaustion are likely with exertion; 41 to 54 °C makes exhaustion probable; above 54 °C heat stroke is imminent.
Does a fan always help?
No. Above roughly 35 °C a fan blows air hotter than your skin and stops cooling effectively.
Heat exhaustion or heat stroke?
Exhaustion brings dizziness, nausea and cool clammy skin. Heat stroke brings confusion, hot dry skin and very high temperature — a medical emergency.
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See all →Updated on June 30, 2026 · by Rafael Rossi · Methodology & sources