Weather.gov API

The United States National Weather Service (NWS) offers an easy to use weather API. To fetch data for a given latitude and longitude, use the following query:

curl -H 'accept: application/geo+json' 'https://api.weather.gov/points/33.3815,-118.4332'

{
  ...
  "properties": {
    ...
    "gridId": "LOX",
    "gridX": 142,
    "gridY": 16,
    "forecast": "https://api.weather.gov/gridpoints/LOX/142,16/forecast",
    "forecastHourly": "https://api.weather.gov/gridpoints/LOX/142,16/forecast/hourly",
    "forecastGridData": "https://api.weather.gov/gridpoints/LOX/142,16",
    "observationStations": "https://api.weather.gov/gridpoints/LOX/142,16/stations",
    ...
  }
}

The response is in GeoJSON format, but there's no need to know the details of that format to use the data.

The NWS operates a number of Weather Forecast Offices (WFO), each responsible for forecasts in a portion of the US. The WFO responsible for that latitude/longitude is .properties.gridId. Each WFO splits the region it's responsible for into a grid. The grid cell corresponding to the requested latitude/longitude is [.properties.gridX, .properties.gridY].

To get the forecast in a machine-parsable, numeric format, use the URL under .properties.forecastGridData. It is also available in human-readable format in 12-hour intervals under .properties.forecast and 1-hour intervals under .properties.forecastHourly. For now, we'll focus on the machine-readable forecast data:

curl -H 'accept: application/geo+json' 'https://api.weather.gov/gridpoints/LOX/142,16'

{
  ...
  "properties": {
    ...
    "temperature": {
      "uom": "wmoUnit:degC",
      "values": [
        {
          "validTime": "2020-06-26T04:00:00+00:00/PT2H",
          "value": 14.444444444444445
        },
        {
          "validTime": "2020-06-26T06:00:00+00:00/PT2H",
          "value": 15
        },
        ...
      ]
    },
    "windSpeed": {...},
    "probabilityOfPrecipitation": {...},
    ...
  }
}

The first thing you'll notice if you try this out is that there's a ton of data returned. Let's focus on one property, .properties.temperature. The unit of the measurement is given under .properties.temperature.uom (°C, in this case). The forecast for each time interval is under .properties.temperature.values. The interval is given in ISO 8601 interval format.

In addition to forecasts, you can request raw observations. Recall that our first query gave a list of observation stations under .properties.observationStations. Let's take a look:

curl -H 'accept: application/geo+json' 'https://api.weather.gov/gridpoints/LOX/142,16/stations'

{
  ...
  "features": [
    {
      "id": "https://api.weather.gov/stations/KAVX",
      "geometry": {
        "type": "Point",
        "coordinates": [
          -118.41456,
          33.40421
        ]
      },
      ...
    },
    {
      "id": "https://api.weather.gov/stations/AIDC1",
      "geometry": {
        "type": "Point",
        "coordinates": [
          -118.3305,
          33.338
        ]
      },
      ...
    },
    ...
  ],
  ...
}

This list includes all the stations within the 2.5 km grid area. We can fetch the most recent observations made by a particular weather station like so:

curl -H 'accept: application/geo+json' 'https://api.weather.gov/stations/KAVX/observations?limit=1'

{
  ...
  "features": [
    {
      ...
      "properties": {
        ...
        "timestamp": "2020-06-26T10:08:00+00:00",
        "temperature": {
          "value": 13.9,
          "unitCode": "unit:degC",
          "qualityControl": "qc:V"
        },
        "dewpoint": {
          "value": 12.8,
          "unitCode": "unit:degC",
          "qualityControl": "qc:V"
        },
        "windDirection": {
          "value": 110,
          "unitCode": "unit:degree_(angle)",
          "qualityControl": "qc:V"
        },
        ...
      }
    }
  ]
}

There's plenty of other data available, so be sure to take a look at the API documentation (click the "Specification" tab). Note that this API barely scratches the surface of what data the National Weather Service has to offer. If you take a look around their website, you'll find many different APIs run by various departments in the NWS, such as the GIS web services and the National Digital Forecast Database.