The DWD products
The German Weather Service runs a network of weather radars and combines their scans into nationwide composites every 5 minutes. It also corrects radar estimates with measurements from its rain-gauge network. Several of these products are published on DWD Open Data, free of charge and without registration. The integration reads five of them.
Radar only: RADVOR and HymecNG
RADVOR is DWD's radar-based nowcast. It takes the latest radar composite, tracks how the precipitation moves, and extrapolates it up to two hours ahead. Every 5 minutes it publishes two products the integration reads:
- RS: 25 rolling 60-minute totals, from the hour just measured to the hour ending two hours ahead. Behind Precipitation last 60 min and the next-hour forecasts.
- RV: 25 steps of 5 minutes, the latest measured one and 24 forecast steps. Behind intensity, peaks, start and end.
RS's hours are the sums of RV's 5-minute steps, in almost every cell exactly.
HymecNG is DWD's hydrometeor classification: every 5 minutes it determines from the radar measurements what type of precipitation is falling, such as rain, drizzle, snow or hail. Behind Precipitation type now.
Radar-only values are fast and finely resolved, but a radar measures in the air above the ground, from the strength of the echo. Its estimate can differ from what a gauge on the ground collects, in either direction.
Gauge-adjusted: RADOLAN
RADOLAN combines the radar composite with the measurements of DWD's rain gauges, so the radar's spatial detail is adjusted to the amounts actually measured on the ground. That takes the gauge reports, so RADOLAN is published about half an hour after its window ends. The integration reads:
- RW: one hour of precipitation. DWD computes it every 10 minutes for the hour ending then; the integration uses the runs ending on the full hour. Behind Precipitation previous hour and Precipitation total.
- SF: 24 hours of precipitation, for windows ending at :50. Behind Precipitation last 24h and yesterday.
The grid
All five products are on the same grid, DWD's "DE1200": 1100 × 1200 cells of 1 km × 1 km covering Germany and a band around it. The integration reads the single cell that contains your location; see Grid cell lookup.
Files and data volume
| Product | Published as | Read |
|---|---|---|
| RS | one archive of 25 HDF5 files every 5 min, under 1 MB to about 17.5 MB depending on rain across Germany | the three hours it needs, by HTTP range requests (about a fifth of the archive) |
| RV | one archive of 25 HDF5 files every 5 min, of similar size | the whole archive |
| HymecNG | one HDF5 file every 5 min | the whole file |
| RW, SF | one small HDF5 file per run | the whole file |
The radar files are decoded on your Home Assistant machine, outside its event
loop, so even a Raspberry Pi stays responsive. No other service is involved:
the integration talks to opendata.dwd.de only.
Terms of use
The data is © Deutscher Wetterdienst and used under the DWD Open Data terms of use. DWD publishes the current status of its radar stations, which explains most gaps in the data.