Consuming weather data from a rest API in Home Assistant

With OpenWeatherMap's api 2.5 being deprecated I went to look for alternatives for the outdoor temperature.​

Vlinder Project API permalink

Via a colleague I stumbled upon the Vlinder project. This citizen science project collects meteorological data in landscapes where we do not have information today. And lucky me, there is a station very close to my home. This means I don't have to buy, install and maintain another sensor for Home Assistant.

A GET call to https://mooncake.ugent.be/api/stations gives a list of all locations with their ID.

To get the weather data from that location you perform a GET call to https://mooncake.ugent.be/api/measurements/ItzXCMYUzi31xyiEZpLxB7ef with ItzXCMYUzi31xyiEZpLxB7ef being the ID of the location.

This will return an array of measurements, the last one being the most recent one. I only listed two here for brevity's sake.

[
  {
    "humidity": 77,
    "id": "ItzXCMYUzi31xyiEZpLxB7ef",
    "measurements": "https://mooncake.ugent.be/api/measurements/ItzXCMYUzi31xyiEZpLxB7ef",
    "pressure": 1005.38,
    "rainIntensity": 0,
    "rainVolume": 0,
    "station": "https://mooncake.ugent.be/api/stations/ItzXCMYUzi31xyiEZpLxB7ef",
    "status": "Ok",
    "temp": 17.6,
    "time": "Fri, 14 Jun 2024 15:25:00 UTC",
    "windDirection": 275,
    "windGust": 6.4,
    "windSpeed": 2,
    "wbgt": null
  },
  {
    "humidity": 77,
    "id": "ItzXCMYUzi31xyiEZpLxB7ef",
    "measurements": "https://mooncake.ugent.be/api/measurements/ItzXCMYUzi31xyiEZpLxB7ef",
    "pressure": 1005.38,
    "rainIntensity": 0,
    "rainVolume": 0,
    "station": "https://mooncake.ugent.be/api/stations/ItzXCMYUzi31xyiEZpLxB7ef",
    "status": "Ok",
    "temp": 17.6,
    "time": "Fri, 14 Jun 2024 15:30:00 UTC",
    "windDirection": 275,
    "windGust": 6.4,
    "windSpeed": 2,
    "wbgt": null
  }
]

Home Assistant Rest Sensor permalink

In Home Assistant you can add sensors that poll a REST api quite easily. Getting the values from the last key proved to be somewhat tricky and only worked with this syntax: value_json[-1:][0].temp

rest:
  resource: 'https://mooncake.ugent.be/api/measurements/ItzXCMYUzi31xyiEZpLxB7ef'
  scan_interval: 300
  sensor:
    - name: 'Outdoor Temperature'
      value_template: '{{ value_json[-1:][0].temp }}'
      device_class: temperature
      unit_of_measurement: '°C'
      state_class: measurement
    - name: 'Outdoor Humidity'
      value_template: '{{ value_json[-1:][0].humidity }}'
      device_class: humidity
      unit_of_measurement: '%'
      state_class: measurement

Then simply add the sensor and you're done!