Well, sort of!

The reason almost everyone starts in Phoenix AZ is partially the lack of rain. It's also a friendly regulatory environment and a dead-simple street grid structure.

Austin TX gets as much rain as, say, Chicago IL, neither is particularly dry. And Atlanta GA is very, very rainy. On paper it actually gets more rain than Seattle WA.

FWIW, LiDAR based autonomous vehicles have figured this out, Waymo can handle all but the heaviest rain (which, TBF, humans also cannot reliably handle)