I have the same problem with DarkSky — the precipitation amounts are wildly different than what my PWS reports (and the station apparently used by DarkSky is less than one mile away). I often see DarkSky reports of small amounts of precipitation when I know there has been absolutely none. This may be caused by morning dew accumulating on that weather station’s rain sensor. I stuck with Zimmerman and the data from my local PWS (delivered locally through a local instance of weatherserver).