California:
Can be good weather, often though vis in the LA Basin is rubbish - 3 statute miles and I don't fly in this without a radar service or traffic information system
Marine layer can be a problem, often it burns off by 11am but can roll in pretty quick. I've been sitting on Catalina Island eating a buffalo burger in clear sunshine, only for 10 mins later to watch the fog roll in.
Often there is an afternoon breeze, which leads to cross winds of 10+ plus at some places. Good for practice but meant it took me 27 hours to solo (but now I'll land with 25kt across the runway and not be too worried
).
Thunderstorms are not too much of a problem in Cali, though go to the desert areas and often you will meet massive thunderstorms in the afternoon. Best fly early out there in the summer.
You may meet heavy turbulence through the mountain passes and in the desert in the summer.
You will have to lean properly too as you'll be meeting high density altitudes.
All in all a great learning experience. You probably won't get any rain in the summer, but don't forget that weather can change everywhere. My brother-in-law who lives in San Diego has been freezing all winter with close to zero temps often!