It rains in SF and there’s even fog… The fog’s name is Karl by the way. It’s also an old coastal city that doesn’t have a sane layout that you might expect from a test area like Arizona. SF is not an easy challenge and there are plenty of self-driving startups that have tried there and failed.
It hasn't rained regularly for years. We're in a bad drought, or as some other people put it, a new normal of very little rainfall.
I have no idea why people minimize level 4 self driving. It would absolutely be enough for most people in those geofenced areas/cities to no longer need a car, would massively drive down drunk-driving deaths, and would be a huge benefit for the blind, the elderly, the rural poor, children, etc.