Emil, thought I would throw my 2 cents into this. I also live in Northern Calif. The controller I replaced used a weather-based system as well. I didn't like the controller for many reasons. However, in the big rains before I replaced it, I saw auto rain delays in the 12-15 day range which were automatic. Especially in clay soli like I have. Water sits a long time even when not visible on the surface.
I don't know much about the old controller and their algorithms. Maybe they a had a great local weather feed. No sensors in the system. It was a WeatherTrak. It was the most difficult to program controller I have ever seen. It had an app for my phone but no programming allowed except standing in front of it, trying to follow a 100 page manual.
I haven't even created a schedule yet for my new Rachio even though all installed and ready to go. I'll probably wait until we see signs of Spring to begin experimentation.