Just to add my 2 cents:
Rachio map shows different types of stations based on what controller you have. Gen 1 and 2 controllers use aerisweather, which owns pwsweather, as the data source, while Gen 3 use Weather Underground.
While it is possible to use a wider selection of weather stations from weather underground with Gen 2 controllers, as @Tintn00 has mentioned, you would need to do a bit of homework.
A good place to start is at wundermap.com, there you can find your location and narrow down the chose to show only stations with rainfall data. In order to do so, you would need to click “All Layers” button on the top right of the map and choose “Precipitation” Layer under the top “Weather Stations” section.
Unfortunately, only station of note I would consider in your area is KCAIRVIN129 (link), here is a write up (link) on what I look for in weather station. As examples of bad stations KCAIRVIN11 (link) has registered 55 inches of rain in Feb 8th (last time it has reported any rain); and KCAIRVIN72 (link) has seem to have forgotten how to reset the daily rain totals this month (last month it seemed to work ok though, maybe a temporary issue).
In any case, once found, you can ask to have the station added to pwsweather, and thereby make it available to Rachio. I’ve done so for the …129 station here (link), so if you want to give it a try, just look for PWS_KCAIRVIN129 in a couple of hours. If there is another station you would prefer to use, just ask, it’s not strictly necessary to make the request in the thread @Tintn00 has linked to, but doing it there makes it less likely that your request will be overlooked.
Cheers,
Gene