You won't see so much rise you go over 4.2v IMO. More likely, you lose a few millivolts sitting 3-4 hrs, and end up about 4.1v, or less. I've never parked my bike, and found it noticeably higher in voltage.
But that's assuming you don't park a bike with a black battery box in full sun for many hours. Drape a white cloth over it if you do.
What I do notice, is less sag on a hot battery than on a cold one. So to my rather crude observations, it's more volts under load, not so much more voltage causing an overcharged situation. This is in a climate where 110F is no big deal, but a cloud going by is.
Maybe I was too vague there. What I am trying to say is, start discharging that battery, and it warms to 100F or so, maybe even more. So what's the diff if ambient is about the same. But put it in a black box in the sun, and you might see 150F, which I would call not good for a battery.
