Humidex Calculator (Calcul Humidex)
Enter air temperature and relative humidity to estimate how hot it feels to the human body.
Tip: Press Enter after typing values to calculate quickly.
What is humidex?
Humidex is a heat index used mainly in Canada to describe how hot weather feels when humidity is included. A standard thermometer only tells you the air temperature, but your body experiences more stress when humidity is high. That is because sweat evaporates more slowly in moist air, reducing your natural cooling system.
In short: humidex combines temperature + humidity into one practical number. This makes it easier to judge outdoor comfort, heat stress risk, and when to reduce physical activity.
Why a humidex calcul is useful
A quick humidex calculation can help you make better daily decisions:
- Plan workouts for cooler periods of the day
- Adjust hydration and rest breaks for outdoor work
- Protect children, seniors, and heat-sensitive people
- Understand why a day can feel much hotter than forecast temperature
- Prepare for heat warnings and avoid heat exhaustion
How humidex is calculated
The standard approach uses air temperature and dew point (or relative humidity converted to dew point). The calculator above accepts temperature and relative humidity, then estimates dew point and applies the humidex formula.
Core humidex formula
Humidex = T + 0.5555 × (e − 10)
Where:
- T = air temperature in °C
- e = water vapor pressure (hPa), derived from dew point
This approach follows common meteorological practice and gives a realistic “feels-like” heat reading for warm, humid conditions.
Humidex interpretation scale
- Below 20: Comfortable to cool for most people
- 20–29: Little or no discomfort
- 30–39: Some discomfort; prolonged activity may feel tiring
- 40–45: Great discomfort; reduce exertion and hydrate often
- 46 and above: Dangerous heat stress; heat stroke risk increases
Example humidex calcul
Suppose the air temperature is 32°C and relative humidity is 65%. The humidex can rise into the upper 30s or around 40 depending on exact moisture content. That means the weather may feel significantly hotter than the raw temperature suggests.
This is why checking only temperature can be misleading in summer. Humidity is often the difference between “warm” and “oppressive.”
Practical heat safety tips
For daily life
- Drink water regularly, even before you feel thirsty
- Wear light, breathable clothing
- Use shade and schedule outdoor tasks early or late
- Take cool-down breaks in air-conditioned or ventilated spaces
For sports and physical work
- Lower intensity as humidex climbs
- Increase rest intervals
- Watch for dizziness, cramps, headache, and nausea
- Stop activity immediately if heat illness symptoms appear
Frequently asked questions
Is humidex the same as heat index?
They are similar in concept, but not identical. Humidex is widely used in Canada, while the heat index is more common in the United States. Both estimate perceived heat using temperature and humidity.
Can humidex be lower than temperature?
In warm-season conditions, humidex is usually equal to or above air temperature because humidity adds stress. At cooler temperatures, the metric is less relevant for comfort decisions.
Does wind affect humidex?
Not directly. Wind can improve cooling perception, but humidex itself is calculated from temperature and atmospheric moisture. For full outdoor comfort, combine humidex with wind, sun exposure, and activity level.
Final thoughts
A fast humidex calcul gives better context than temperature alone, especially during hot and muggy weather. Use the calculator above before outdoor work, exercise, travel, or events. Understanding humidex helps you stay productive, comfortable, and safer during heat episodes.