The official start of Summer 2014 is Saturday, June 21, 2014 at 6:51 a.m. EDT which is 3:51 MST where I live.
Of course summer really starts on Memorial Day weekend. Our weather has been pretty nice in Prescott cool nights, mornings and evenings. Hot mid-day, 92 as I type this at 2:30 on Friday (I set the post to appear on the blog at the time of the summer solstice). The humidity as been between low and nonexistent, so the evaporative cooler has been keeping the house comfortable during the day at much less cost than using the air conditioner.