Wind Chill Calculator
Wind chill explains why a cold day can feel bitter the moment the wind picks up, and this calculator turns the air temperature and wind speed into the feels-like figure that actually matters when you head outdoors. Your body constantly warms a thin layer of air right against your skin, and that layer acts like insulation; wind blows it away and replaces it with cold air over and over, so heat is carried off your body far faster and the air feels much colder than the thermometer says. Enter the temperature in degrees Celsius and the wind speed in kilometres per hour, and the calculator returns the wind chill along with a frostbite and exposure risk guide, updating as you type. It uses the standard wind chill formula adopted across New Zealand, Australia and North America, which applies when the temperature is at or below 10 degrees and the wind is above about 5 kilometres per hour, the conditions where the effect is real and worth knowing. The practical value is in staying safe and comfortable. Wind chill is a much better guide than the raw temperature for deciding how to dress, how long it is safe to be exposed, and when conditions tip toward frostbite or hypothermia. That makes it especially useful in New Zealand for trampers, hunters, skiers and anyone heading into the alpine or exposed coast, where a brisk southerly can drag the feels-like temperature well below the reading and turn a manageable day into a dangerous one. It is also a clear way for students to understand convective heat loss. The formula and a worked example are explained clearly below, so check it before you head out.
How it works
The wind chill is 13.12 plus 0.6215 times the temperature, minus 11.37 times the wind speed to the power 0.16, plus 0.3965 times the temperature times the wind speed to the power 0.16, with temperature in degrees Celsius and wind in kilometres per hour. It applies for temperatures at or below 10 degrees and winds above about 5 km/h; outside that range the feels-like temperature is just the actual temperature.
Worked example
At 5 degrees with a 20 km/h wind, the wind speed term (20 to the power 0.16) is about 1.62. Putting the numbers in gives 13.12 plus 3.11 minus 18.36 plus 3.20, which is about 1.1 degrees. So a 5-degree day with a moderate breeze feels close to freezing.