In veg I wouldnt stress out about it too much, like others said it will make them drink more so cut nutes down a little. Ive vegged plants in my attic before with no ventilation and just fans, it would regularly get to 95 degrees F which is 35 C and they didnt skip a beat. It would sometimes get to 100, they would droop some but they snapped out of it once it cooled down some. I wouldnt reccomend it in flower anytime passed 2 weeks after flip.