need is a strong word. i don't use domes at all
:P my early growth probably suffers slightly from it, but not too significantly. not even certain i can distinguish the effect.
you may need to take them off and put them back on in a cycle initially. if they fall over, just prop them up with a toothpick or whatever you got. As they get more robust you leave it off for longer durations.
90 degree temps may be an issue for a seedling. If they've started inside, the transition may be longer. it'll have to adapt to a much more intense environment.