I don't like to tow at night.
If my trip will be in 90 plus heat or a big climb I will leave just before dawn when it's cool and try to reach my destination by noon to avoid the hottest part of the day.
For several years in September (average 80 plus degree daytime temps) we would head for a campground in the western Sierra Mountains of California. The trip included a climb from 500ft sea level to over 5000 ft on a 6 to 10% grade. 21 miles of switchbacks to get to the top of the grade. It would take about an hour in first gear. A real strain on the truck. We would hit the hill just as the sun was coming up (60 degree heat).