I'm on my bike from 4:45 to 5:10 most mornings, but that's just my commute.
For long rides I really like getting started a few hours before dawn. Roads are quiet, you can see dawn unfolding little by little, you see animals...
Rudi, another benefit you allude to for most people that live in an urban area: you get out of town and into the countryside before traffic picks up.
The OP's intent is to beat the heat. Three timese in the past year I started pre-dawn for another reason: to get a ride done earlier or make a cut-off time. In my "What could possibly go wrong?" tour of the Bay Area right after Christmas 2018 I was leaving from near Santa Cruz to get back over the Coastal Range and to SFO for a late afternoon flight out. Even though the pre-dawn start was very chilly, watching the sun come out over the coast and slowly warming my body up, no traffic on Hwy 1, the views...
We typically think of the golden hour, that time when the sun is coming across the atmosphere at a low angle and giving light a redder, warmer, softer tone. There are actually two golden hours, one just after sunrise, the other after sunset.
This got me thinking of another pre-dawn start to a ride - with @
rhm riding through eastern Long Island to catch a noon ferry to Connecticut on the way to French Fender Day.
