Hey! There's a difference between ambient and radiant heat. They will take short periods with heat up to 30-35 C without damage, but that will stress them and make them drink a lot to cool down. I would suggest you keep the temps under 30 C, ideally in the 24-28 C range. In flowering high temps negatively effect potency. https://www.greenpassion.org/index.php?/topic/16445-ambient-heat-vs-radiant-heat/ Here are some experiences with high temps: http://boards.cannabis.com/plant-problems/185657-max-grow-temp-allowed.html
my ambient is running around 85 tonight with a high of 92 and a low of 83. under the light is MUCH hotter, +/- 95 and a sunburn. relative humidity, RH, is being kept at 40 to 45% and co2 is 1750ppm. girls are lovin' it.
Keep it under 90* F for an extended period of time Higher than that can slow to stop all growth If temps go above that use a fan to cool the plant or move it away from direct light Shade or the outer perimeter of your light