How hot is too hot in a prop dome/tray setup? for germing seeds

How hot is too hot in a prop dome/tray setup? for germing seeds

RH and temp? RH can be basically 100% right? is that as soon as the tap root pops, im using root riot plugs, so i put tap root down, put in the prop tray, dome on, with heat mat under it. Does all that sound alright first off? And then how hot is too hot?

Thanks!!

I germ at 80, never checked the RH but im sure its around 100%, I keep em covered til they are above ground and shed the seed and then uncover em and put em under some cfls with a light breeze from a fan for a week. I dont know how hot is too hot but 80 has never failed me