How I use my cumulative rainfall sensor data

[edgimar]

@jeroenterheerdt, thanks for version 2025.7.2! The user-interface is much improved, and the fact that it allows you to view the weather data is very helpful for understanding / diagnosing issues. In my case, it turns out that my weather sensor provides a cumulative sum (over a very long period of time - maybe a year or more?) of precipitation. By seeing the weather data, it became clear that the integration is expecting (if I understand correctly) an accumulated amount since the last time that the sensor was polled, and not a long-term cumulative value. Using the cumulative value led to the bucket always (incorrectly) appearing quite full.

To resolve this problem (for a poll frequency of once per hour), I created and now use a 'derivative sensor' helper with a time window of 1 hour. Since I suspect many weather stations provide the same kind of "cumulative over a long time" data, it might make sense to provide an option in the sensor-group configuration to indicate whether to treat the provided sensor's value as a cumulative value or a delta. In fact, a cumulative value might be more sensible as a default since it reduces the coupling between the integration's poll-rate and the sensor's difference window size.