Weather Forecast in Home Assistant

What to do, if

{{ state_attr('weather.openweathermap', 'forecast') }}
{{ state_attr('weather.home, 'forecast') }}

only return null ?

First, test

service: weather.get_forecasts 
 data:
   type: hourly
 target:
   entity_id: weather.openweathermap # or weather.home

in Homeassistant dev tools/serices YAML Mode if you see forecast results.

template:
- trigger:
      - platform: time_pattern
        hours: /1
      - platform: homeassistant
        event: start
    action:
      - service: weather.get_forecasts
        data:
        # type hourly gibt einem für alle drei stunden einen forecast zurück
          type: hourly
        target:
          entity_id: weather.openweathermap
        response_variable: hourly
    sensor:
      - name: Temperature forecast in 3h
        unique_id: temperature_forecast_next_hour
        state: "{{ hourly['weather.openweathermap'].forecast[0].temperature }}"
        unit_of_measurement: °C
        attributes:
          temperature: "{{ hourly['weather.openweathermap'].forecast[0].temperature }}"
          datetime: "{{ hourly['weather.openweathermap'].forecast[0].datetime }}" 
          humidity: "{{ hourly['weather.openweathermap'].forecast[0].humidity }}"

based on How To Use Hourly Forecast Information (Since 2024.3.0)

Article relase date: (02.05.2024) / Last update: (03.05.2024)