This time of year the temps can be way too hot for herps, especially corn snakes that don't the heat like BPs do. "Ambient" sounds harmless but can kill pets.
And just like dogs in hot cars, they might survive but with neurological damage. Why take that chance?
Using an insulated container isn't a big ask, to me it's just better safe than sorry. We humans are blessed with foresight, it's a shame to waste it. And if your
budget is tight, you'll often find styrofoam shipping containers in thrift stores VERY cheaply. (they're also superb to keep in your trunk, for carrying ice cream
home from the grocery store...)