Since I’m thinking about re-activating my opensprinkler, I thought I’d chime in.
I’ve been comparing my own weather data to OWM and Climacell for quite a while now and must say that both are equally bad. Big jumps in temperature (and especially humidity), mostly. Not comparable in quality to DarkSky by a mile (yes, I’m also sad that will go away).
Rain is difficult to say as it’s usually thunderstorms around here, and those tend to be rather localized.