Garages in the deserts can reach temperatures in excess of 40 deg C (104F) in the daytime and don't really drop below 27 deg C (about 80F) at night. (I didn't have a temperature gauge on me at the time but all I knew was that it was -hot- in there. Yeah it was 35C (95F) outside but it felt like 44 deg C (about 110F) inside the garage.
Those are summertime quotes though. I didn't stay for winter.
Those temps are little too hot for long term storage in my personal opinion. All my electronic stuff is stored inside where there is at least a chance of maintain a 24 deg C (~75F) air conditioned area. Not to mention that deserts can get freakin' cold in the wintertime -- no thanks.