By default, Rachio will select a nearest Airport station, so you could simply do the same thing and select an airport station nearby.
That being said, I feel that your interest lies in getting rid of any effect a selected weather station may have on your irrigation, in which case you can simply setup a manual schedule and turn off any weather intelligence options you would have access to (essentially getting the same effect).
Rachio, being an intelligent controller, makes good use of weather data. In order to get the most out of it I advise trying to find a good, local, weather station. If personal weather stations available to Rachio by default are too far away / provide inaccurate data, than I recommend you check out weatherunderground.com to see if any good stations are closer to where you are. Here is a writeup (link) about choosing a good weather underground station. And beta.wufyi.com is one of the ways that data from weather underground can be transferred to pwsweather.com for free using a free cron-job.org account. If you run into any trouble / have any questions, feel free to ask.
In summary, it is possible to turn off the effects of weather data on your irrigation, but perhaps a better approach would be to find a closer weather station.