DWD Nowcast

DWD nowcast is a Home Assistant custom integration that provides a minute-by-minute precipitation nowcast for a configured location based on Deutscher Wetterdienst (DWD) Open Data.

Follow this link for the license terms of the DWD: https://opendata.dwd.de/README.txt

What is the difference between a forecast and a nowcast

Forecasts are model-based predictions that try to predict the weather over the next days. They use large- scale weather models and calculate larger trends such as temperature changes, weahter fronts, and development of storms.

Nowcasts focus on the next upcoming minutes (upo to an hour in the case of this integration) and are based on radar images showing the position (and movement over multiple images) of precipitation cells. This makes them more accurate for short-term rain prediction.

If you want to know it will start to rain close to NOW, nowcasts are more reliable.

About this integration

• Provides a 60-minute precipitation nowcast as a Home Assistant service
• Source: DWD Open Data radar nowcast (Radarkomposit RV)
• DWD Update interval: every 5 minutes
• Time resolution: 5 minutes, internally interpolated to per minute values by the integration
• DWD Forecast resolution: approximately 1 km grid
• Location mapping: Configured latitude/longitude is mapped to the nearest grid cell

This integration focuses on minute-by-minute precipitation ONLY. It does not expose standard weather conditions, temperature, or long-term forecasts. For full weather data from DWD, use this dedicated DWD weather integration: https://github.com/FL550/dwd_weather

HACS installation

Click this button

or

1. In HACS, go to Integrations.
2. Open the menu (top right) and choose Custom repositories.
3. Add this repository URL and select Integration as category.
4. Install DWD nowcast.
5. Restart Home Assistant.
6. Add the integration via Settings > Devices & Services.

Manual installation

1. Copy the custom_components/dwd_nowcast directory into your Home Assistant custom_components directory.
2. Restart Home Assistant.
3. Add the DWD nowcast integration in Settings > Devices & Services.

How to use

The integration registers a get_minute_forecast service for its weather entity:

action:
  - service: dwd_nowcast.get_minute_forecast
    target:
      entity_id: weather.dwd_nowcast
    response_variable: minute_forecast

Besides the top level key with the service signature, the service response is compatible with the OpenWeatherMap's get_minute_forecast format:

weather.dwd_nowcast:
  forecast:
    - datetime: "2026-01-26T19:10:00+00:00"
      precipitation: 0
    - datetime: "2026-01-26T19:11:00+00:00"
      precipitation: 0
    - datetime: "2026-01-26T19:12:00+00:00"
      precipitation: 0
    ...

Data format

Attention: The returned precipitation values are converted to mm/h as strength of rain. This has been done to be compatible to the OpenWeatherMap integration / action. The DWD itself returns mm values for ammount of rain in the given time period.

Notes and limitations

• DWD nowcast data is updated every 5 minutes and typically appears a few minutes after the timestamp in the filename.
• DWD RV values represent 5-minute accumulations in mm and are converted to mm/h to match the OpenWeatherMap-compatible response format.
• If the location is outside the DWD RV grid, the forecast list is empty.
• Radar nowcasts can be inaccurate for very small or fast-changing precipitation.