Wind Chill vs Humidex
Both the wind chill factor and the humidex are apparent-temperature indices: they convert raw weather observations into a number that describes what the conditions actually feel like to a person. That is where the similarity ends. The wind chill factor, built on the U.S. National Weather Service equation, is the cold-weather index: it combines air temperature with wind speed to estimate the cooling effect on exposed human skin. The humidex, built on the Environment Canada formula, is the warm-weather index: it combines air temperature with humidity to estimate how hot and humid conditions feel. Each has its own equation, inputs, and official scope, and neither should be used outside the conditions it was designed for.
This page compares the two calculators so you can tell which index matches the weather you are evaluating. It is informational, not a forecast or medical guidance.
What each calculator does
The wind chill calculator applies the NWS wind-chill temperature equation from air temperature and wind speed. Inputs in other units are converted exactly to Fahrenheit and miles per hour before the equation runs, and the calculator returns a value only when the converted temperature is at or below 50°F and the converted wind speed is above 3 mph — exactly 50°F is included, exactly 3 mph is not. The NWS model is based on adults, assumes no effect from sunshine, and uses wind speed adjusted to an average height of 5 feet from standard 33-foot anemometer readings.
The humidex calculator applies the Environment Canada humidex equation from air temperature and dew point, both in Celsius. It reports a value when the air temperature is at least 20 °C and the humidex is at least one degree above the temperature, and it maps the result to the official comfort categories: 20–29 little discomfort, 30–39 some discomfort, 40–45 great discomfort (avoid exertion), and 46+ dangerous.
Side-by-side comparison
| Feature | Wind chill calculator | Humidex calculator |
|---|---|---|
| End of the temperature scale | Cold (at or below 50°F) | Warm (at or above 20°C) |
| Origin | National Weather Service (U.S.) | Environment Canada |
| Inputs | Air temperature and wind speed | Air temperature and dew point |
| Equation basis | NWS wind-chill formula, run in °F and mph | H = T + 0.5555 × (6.11 × e^(5417.7530 × (1/273.16 − 1/(273.15 + Td))) − 10), run in °C |
| Scope condition | Temperature ≤ 50°F and wind speed > 3 mph | Air temperature ≥ 20 °C and humidex ≥ temperature + 1 |
| What it models | Human-face cooling effect of wind | Heat stress from temperature plus humidity |
| Output | Wind-chill temperature, whole-degree display | Humidex value plus comfort category |
When to use which
Use the wind chill calculator when the weather is cold and windy — that is the only range where the NWS equation is defined — and when you have a wind speed measurement, not just temperature. Use the humidex calculator on hot, humid days when you have or can estimate a dew point, which is the humidity measure the Environment Canada formula actually uses. The site’s heat index calculator covers a third apparent-temperature model for the U.S. convention that combines temperature with relative humidity, so it is the right tool when you have relative humidity rather than dew point.
Whichever index you use, remember that both are estimates of how conditions feel to people, not measurements of what a surface or object will do, and neither page provides a forecast or individualized health advice.
Where to start
- Wind chill calculator — NWS cold-end index from air temperature and wind speed, valid at or below 50°F with wind above 3 mph.
- Humidex calculator — Environment Canada warm-end index from air temperature and dew point, with official comfort categories.
Informational note: This page is an educational comparison of two apparent-temperature indices. It is not a weather forecast, emergency guidance, or medical advice. Weather agencies can update equations and reporting thresholds, and personal risk depends on health, clothing, exposure time, and conditions these indices do not capture. Confirm current guidance from the National Weather Service or Environment and Climate Change Canada before acting on a reading.