Check out http://droughtmonitor.unl.edu/
You can look at the change maps or the drought history. Northern Cali is no longer in a drought, and most of the worst drought is gone in the state. D2-D4 in 2016 was 81% of the state, and this year it is 11% with very little D3 and no D4 conditions. Last year D4 covered 38% of the state.
If I were going to guess, I would say it is the net effect of all the EVs and solar, and wind they put in that lowered the temp enough for it to rain, but I am sure that isn’t the whole story if it even is part of the story.