{
  "id": "wind-chill",
  "version": "9f70199993b9",
  "status": "published",
  "name": "Wind Chill Calculator",
  "question": "What is the wind chill?",
  "summary": "Computes the wind chill temperature (how cold it feels on bare skin) from the air temperature and wind speed with the 2001 NWS and Environment Canada formula, in °F and °C.",
  "category": "physics",
  "subcategory": "weather",
  "url": "https://www.acalculator.org/physics/wind-chill-calculator",
  "markdown": "https://www.acalculator.org/physics/wind-chill-calculator.md",
  "kind": "function",
  "method": "WCT = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T·V^0.16, with T in °F and V in mph, for T ≤ 50 °F and V above 3 mph (NWS and MSC, 2001).",
  "assumptions": [
    "The wind speed is at the standard height of 10 m (33 ft), as weather reports give it; the formula reduces it to face height.",
    "Bare face skin, walking into the wind at about 3 mph, with no sun; the NWS notes that bright sunshine can make it feel 10 to 18 °F warmer.",
    "Defined only at 50 °F (10 °C) or colder and at winds above 3 mph (4.8 km/h)."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "t": {
        "title": "Air temperature",
        "description": "The air temperature, 50 °F (10 °C) or colder.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "temperature",
        "minimum": 199.8166666666667,
        "maximum": 322.03888888888895
      },
      "v": {
        "title": "Wind speed",
        "description": "The wind speed at the standard 10 m (33 ft) height, as weather reports give it: above 3 mph.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "speed",
        "minimum": 0,
        "maximum": 111.76
      }
    }
  },
  "outputs": {
    "windChillF": {
      "label": "Wind chill (°F)",
      "description": "How cold it feels on bare skin, in °F.",
      "format": "number"
    },
    "windChillC": {
      "label": "Wind chill (°C)",
      "description": "The same wind chill in °C: (°F − 32) × 5 ÷ 9.",
      "format": "number"
    },
    "colderBy": {
      "label": "Feels colder by (°F)",
      "description": "The air temperature minus the wind chill, in °F.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "t": 266.48333333333335,
      "v": 6.7056
    },
    "outputs": {
      "windChillF": 6.218885266083872,
      "windChillC": -14.322841518842292,
      "colderBy": 13.781114733916128
    },
    "text": "At 20 °F with a 15 mph wind, the wind chill is 6.2 °F (-14.3 °C)."
  },
  "examples": [
    {
      "given": {
        "t": 255.37222222222223,
        "v": 6.7056
      },
      "expect": {
        "windChillF": -19.397954107996384,
        "windChillC": -28.55441894888688
      },
      "source": "NWS Wind Chill Chart (2001): −19 °F at 0 °F and 15 mph; hand calculation in content.mdx: 35.74 − 35.75 × 15^0.16 = −19.40 °F"
    },
    {
      "given": {
        "t": 266.48333333333335,
        "v": 6.7056
      },
      "expect": {
        "windChillF": 6.218885266083872,
        "windChillC": -14.322841518842292,
        "colderBy": 13.781114733916128
      },
      "source": "NWS Wind Chill Chart (2001): 6 °F at 20 °F and 15 mph; hand calculation in content.mdx: 35.74 + 12.43 − 35.75 × 1.5423 + 0.4275 × 20 × 1.5423 = 6.22 °F"
    },
    {
      "given": {
        "t": 249.8166666666667,
        "v": 13.4112
      },
      "expect": {
        "windChillF": -39.446669956722786
      },
      "source": "NWS Wind Chill Chart (2001): −39 °F at −10 °F and 30 mph; hand calculation in content.mdx"
    },
    {
      "given": {
        "t": 253.14999999999998,
        "v": 8.333333333333334
      },
      "expect": {
        "windChillC": -32.536432773693214
      },
      "source": "Environment and Climate Change Canada, Wind chill index table: −33 at −20 °C and 30 km/h (its °C form, 13.12 + 0.6215T − 11.37V^0.16 + 0.3965T·V^0.16, gives −32.57); hand calculation in content.mdx: −4 °F and 18.64 mph give −26.57 °F = −32.54 °C"
    }
  ],
  "sources": [
    "National Weather Service, Wind Chill Chart and formula (2001): WCT = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, defined at or below 50 °F and for winds above 3 mph; bright sunshine may raise it by 10 to 18 °F. https://www.weather.gov/safety/cold-wind-chill-chart",
    "Osczevski, R., and M. Bluestein (2005). The New Wind Chill Equivalent Temperature Chart. Bulletin of the American Meteorological Society 86(10), 1453–1458. https://doi.org/10.1175/BAMS-86-10-1453",
    "Environment and Climate Change Canada, Wind chill index: the metric formula and table. https://www.canada.ca/en/environment-climate-change/services/weather-health/wind-chill-cold-weather/wind-chill-index.html",
    "NIST Special Publication 811 (2008), 4.2.1.1 and B.8: °F = 1.8 × °C + 32; 1 mph = 0.44704 m/s; 1 km/h = 1/3.6 m/s; 1 knot = 1,852/3,600 m/s. https://www.nist.gov/pml/special-publication-811"
  ],
  "related": [
    "heat-index",
    "dew-point"
  ],
  "changelog": [
    {
      "date": "2026-09-30",
      "note": "Metric heads the result with the wind chill in °C and names °C first."
    }
  ]
}