Timespan without precipitation

Timespan without precipitation (days) counts the time since it last rained enough at your location. It suits watering automations: "water the garden after three dry days".

Attribute	Meaning
hours_without_precipitation	The same streak in hours; null until the counter has started
dry_since	The time the counter counts from, ISO-8601 UTC: the end of the hour that last reset it, or on a new install the start of the dry period DWD's data shows

A new install does not start at zero: the counter starts as far back as DWD's gauge-adjusted analyses prove it was dry, up to 24 hours (when Precipitation last 24h stayed below the threshold). It keeps counting across restarts.

What resets it

Two options decide it:

• Rain that resets the count (default 1.0 mm): a past-hour total at or above this resets the counter. It is an amount within the hour, not a rate.
• Measured with picks which past-hour total is compared:

Source	Updated	A reset shows	Notes
Radar and rain gauges (RW)	every 10 min	30 to 40 min after the rain	Corrected with rain gauges, more accurate. Default for new installs
Radar only (RS), the hour of Precipitation last 60 min	every 5 min	a few minutes after the rain	Radar only, noisier

Both sources are the rain of the last 60 minutes: RS a new hour every 5 minutes, RW every 10, as DWD reruns its analysis for the hour ending then. A reset moves dry_since to the end of the hour that reached the threshold. So with either source, rain keeps resetting the counter after it has stopped, for as long as what fell inside the latest hour still reaches the threshold: up to an hour. The counter then starts at the end of the last such hour, at most an hour after the rain stopped.

Installs set up before the source option existed keep RS, so upgrading changes nothing. When you switch, the counter keeps its value.

There is deliberately no fallback to the other product: while the selected one is unavailable, so is the counter.

Restarts and downtime

While Home Assistant is down, nothing is measured. On startup the counter catches up from the RADOLAN analyses:

• if the latest RW hour reached the threshold, the counter restarts at the end of that hour;
• otherwise, if SF's past 24 hours did, it restarts at the start of those 24 hours, since SF cannot say when within the day it rained.

The hours of the downtime are then also checked one by one, as described next, which places rain within the downtime to the hour.

Outages: hours without data are checked later

A reading without data (unknown, for example while a radar is out of DWD's composite) cannot reset the counter, so rain in such a gap would be missed. When the source has had no data for your location for more than an hour, the clock hours it missed are checked against DWD's gauge-adjusted hour (Precipitation previous hour) once it reports again: an hour that reached the threshold resets the counter to that hour's end. The same check covers the time Home Assistant was down, and time DWD failed to publish.

The hours are fetched in the background, newest first. DWD keeps them for two days, so an older gap is not checked. See ADR 0011 for the reasoning.