Currently Rachio just blindly uses the reported weather station data. However, especially with PWS data, somtimes the data is inaccurate.
Several times the nearest wether station has reported 6" rain in the middle of summer, and Rachio has decided to kill all my plants by not watering for a week.
It’s pretty trivial in this case to see that all the other nearby wether statios reported zero rain, and 6" is far outside the band of historic rainfall in California summers. So it should be possible to automatically ignore the fautly data point or automatically blacklist the weather station.
Running any FLEX is not an “install and forget” scenario. Where I live we have very localized rainfall during summer time, so I keep an eye on 3 weather stations and e.g. have eliminated one for spotty and consistent underreporting. As @robertokc said I too kept the fortunately close airport as my default, and use the others to adjust manually if there is a big local discrepancy.
What I sometimes do is when traveling and can’t judge what happened during the day, is have a look in the evening at the cumulative data on the Wundermap in my area. You can change the icon just above the map from temperature to precipitation and then you see who reports what. In the example attached there was obviously no rainfall this morning, and you can see that one guy still reports .11 inches. Hope this helps going forward.