Read the wind chill before going out
−5 °C in a gale is not −5 °C. The NWS formula turns temperature and wind into the number your skin actually feels.
Tools used in this guide
The job
Moving air strips the thin warm layer around skin, so wind makes cold bite harder. Wind chill quantifies it — the number weather services report alongside the thermometer.
Temperature + wind
Enter air temperature and wind speed (km/h, mph, or m/s). Below 4.8 km/h the air counts as calm and the tool returns the air temperature — the formula simply does not apply to still air.
Worked example
−10 °C at 30 km/h feels like about −19.5 °C — frostbite territory on exposed skin within ~30 minutes. The same −10 °C in still air is just −10 °C; the wind alone removed 10 degrees of comfort.
Where it stops
Valid −60…10 °C, wind to 200 km/h. It models exposed skin — layering and sun exposure change the felt number. Objects do not cool below air temperature no matter the wind.