It does get extremely hot in the summer, but it's a dry heat and as a result doesn't feel as hot as it really is. I'm originally from Southern California and although the weather was once beautiful there, it has now become just as hot as Arizona. I experience the same weather here in Mesa, Arizona as I do in Los Angeles County, minus the humidity. My mother still lives in Southern California and we constantly compare temperature and weather conditions. 95% of the time it's the same except for a few degrees cooler in California in the summer months, but my central AC makes up for that, while my mother and most people that live in her area go without central AC.
It also rains in the summer, which I find amusing. The sun is out, but theres rain... I like it!