Dear BK,
It's a good thing you don't live in Phoenix. In the summer here, people get up EARLY -- before the heat. If you don't get your yard work started before 6 a.m., it is too hot. In fact, I told the next-door-neighbor that if it's ok with her neighbor on the other side, she should have her husband/brother/SO/whoever get started at 5 a.m.