Wind chill calculator
See how cold the wind makes the air feel on bare skin: −10 °C with a 20 km/h wind feels nearly 8 degrees colder, worked out with the 2001 metric formula used by North American forecasters. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Creativity
- -10
- Wind speed
- 20
- Wind chill
- -17.8605843444 celsius
- Feels colder by
- 7.8605843444
- Wind speed power
- 1.6149712647
- Formulation
- nws_jag_ti_2001
Wind chill is the perceived temperature that exposed skin feels when cold air is moving, not the thermometer reading itself. A winter walk at minus five degrees Celsius can feel far colder once a stiff breeze strips the thin layer of warm air that otherwise sits against the body. This wind chill calculator applies the current National Weather Service and Environment Canada metric formula: air temperature in Celsius and wind speed in kilometres per hour go in, and a feels-like temperature in Celsius comes out.
What modern wind chill temperature measures
After wind-tunnel work on facial heat loss, the Joint Action Group for Temperature Indices published the operational formula that the National Weather Service and Environment Canada adopted in 2001. In metric units the expression is W equals 13.12 plus 0.6215 times T minus 11.37 times V to the power 0.16 plus 0.3965 times T times V to the power 0.16, where T is air temperature in degrees Celsius and V is wind speed in kilometres per hour, conventionally reported at about ten metres above the ground.
The 0.16 exponent is empirical: perceived cooling rises quickly as still air becomes a light breeze, then each extra kilometre per hour adds less. Subtracting W from T shows how many degrees colder the wind makes the air feel on bare skin. This capability evaluates that exact identity with twelve-decimal rounding so tests and widgets stay byte-stable.
It does not fold in humidity, solar radiation, or clothing, and it does not convert miles per hour for you; send kilometres per hour. Use it when you need the current public-weather feels-like number, not a historical cooling-power recreation.
Who relies on the wind chill number
School districts, ski areas, and municipal emergency desks need a deterministic oracle that turns a station temperature and a wind reading into the same feels-like number that public weather products quote, without spreadsheet rounding fights across classrooms and duty officers. Winter-sports and hiking applications show wind chill beside air temperature so users dress for exposed skin, not for the forecast high, and logistics teams use the same number when they decide whether a loading dock crew stays outside.
Facilities and construction safety programs log wind chill against work-rest guidance when crews are outdoors in polar air, pinning the rounded output in their records. Keep temperature in Celsius, keep wind speed in kilometres per hour and non-negative, pin rounded outputs in tests, and you get reproducible perceived temperatures for courses, dashboards, and edge workers without standing up a full meteorological library of your own. This landing is the modern equivalent-temperature tool; the historical 1945 cooling-power index is a different search and a different capability.
What you can do with it
School and workplace cold-weather decisions
Turn a station temperature and wind reading into the public feels-like number before delaying recess, rotating outdoor crews, or posting a wind-chill warning.
Winter sports, hiking, and trip planning
Show wind chill beside air temperature so skiers, hikers, and drivers dress for exposed skin rather than the forecast high alone.
FAQ
What formula does this wind chill calculator use?
The result is a perceived temperature in Celsius.
Which units should I send for air temperature and wind speed?
Temperature in degrees Celsius and wind speed in kilometres per hour.
Is this the same as the 1945 Siple and Passel wind chill index?
The 1945 Siple–Passel index is a cooling-power measure in kcal/(m²·h) with different inputs and units.
What is the wind chill at −10 °C with a 20 km/h wind?
It feels nearly 8 degrees colder than the thermometer: exposed skin loses heat as if the calm air were that much colder. The calculator also lists each step, from the wind power to the final subtraction.
Does wind chill include humidity, sunshine or clothing?
No. The result depends only on air temperature and wind speed. Humidity, solar radiation and clothing are left out, so treat the number as the standard public feels-like value for exposed skin, not a personal comfort forecast.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/weather/wind-chill \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"temperature":-10,"wind_speed":20}'const res = await fetch("https://api.kit.forhosting.com/weather/wind-chill", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"temperature": -10,
"wind_speed": 20
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/weather/wind-chill",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"temperature": -10,
"wind_speed": 20
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/weather/wind-chill", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"temperature":-10,"wind_speed":20}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"temperature":-10,"wind_speed":20}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/weather/wind-chill", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"temperature": -10,
"wind_speed": 20
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "weather.wind_chill",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Negative wind speed is rejected as invalid_input so automation never invents a cooling rate from a signed gust.
What modern wind chill temperature measures
The modern wind chill temperature is an equivalent still-air temperature: the air temperature which, in calm conditions, would produce the same rate of heat loss from exposed facial skin as the actual combination of cold air and wind. It is a feels-like temperature in degrees Celsius, not a cooling-power index in kilocalories per square metre per hour, and it is not the 1945 Siple and Passel product used in some historical station logs.
Input contract, units, and error behaviour
Wind speed must be non-negative: a negative gust has no physical meaning in this model and is rejected so scripts never compute a heating rate from a signed speed. Example: minus ten degrees Celsius with twenty kilometres per hour of wind yields a wind chill several degrees colder than the thermometer. POST a JSON object with two required finite numbers. temperature is the air dry-bulb temperature T in degrees Celsius; accepted aliases are t, temp, temp_c, temperature_c, and air_temperature. wind_speed is the wind velocity V in kilometres per hour; accepted aliases are v, wind, speed, wind_kmh, and speed_kmh. Convert from metres per second by multiplying by 3.6, or from miles per hour by multiplying by 1.60934, before you call the endpoint so the 0.16 power sees the units the formula was fitted on. Both fields may arrive as JSON numbers or numeric strings; missing, blank, or non-finite values fail with invalid_input naming the field. Air temperature may be positive or negative; the operational charts are most accurate at or below ten degrees Celsius with wind at or above 4.8 kilometres per hour, and the response flags in_operational_range for that window, but this endpoint still evaluates the algebraic formula for other finite pairs so callers can plot the full surface. On success the body echoes the rounded inputs, returns wind_chill as the perceived temperature in Celsius, reports feels_colder_by as T minus W, exposes wind_speed_power as V to the 0.16, and includes formula, equation, and steps strings for teaching interfaces. Failed validation is not billed; successful analytic calls use the published $0.002 base price with no model tokens and no outbound network.
Integration use cases
Widgets, dashboards, and API automation
Power a wind chill calculator landing or a safety dashboard whose free browser results match the prepaid API at $0.002 per successful call.
Technical questions
Why does negative wind speed fail the request?
Wind speed must be non-negative. A negative gust is not a physical input to the wind-chill model, so the task fails with invalid_input and is not billed.
What does a wind chill API call cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.