We hiked Yosemite in July of last year, and the weather was perfect. It got up in the high 70s/low 80s during the day and was 40-50 degrees at night (perfect sleeping weather!). I'm personally not a fan of camping when it's too warm at night, and anything warmer than 55 degrees makes me sweat inside my sleeping bag. I slept in shorts and a tshirt inside my bag during the Yosemite trip and was extremely comfortable.