I think this whole idea is being over-thought here. Just use a little common sense. Don't set the snake down on anything like asphalt or concrete or metal that has been sitting in direct sun for a long time. It's not a 90 degree day that cooks an egg...it's the heat the asphalt has been absorbing and building up. You can't cook the same egg on the grass.
It's ok to set the snake in the grass...shade or sun...for a few minutes, like for a photo session or something like that. Beyond that, there's really no point to it. They don't need to "soak up sunlight" like a lot of lizards or other reptiles might. And they're not like dogs that you can just let loose in the backyard for some playtime and then bring them back in when they're done.
If you want to take your snake out for pictures, or for whatever other reason you might have...it's ok. Just be careful...never let them out of your control or your sight for even a moment...it will astonish you how FAST they can suddenly move and disappear. Any small hole or opening will be an almost certain invitation for them to explore and disappear into.
So just....be careful!