I am having a similar problem although only to about 85 degrees, the best solution is to vent the closet outdoors if possible. I am installing an inexpensive through-the-wall exhaust fan, and another small fan pulling air in from my bottom vent.

Even if you can't modify the walls, more/cooler airflow is the answer. As someone said above, your plants will either die or simply stop developing because photosynthesis slows/stops over 90 while the plant just tries to transpire as much water as possible.

Good luck.
MajMike Reviewed by MajMike on . Reducing Closet Temperature We have 2 plants going in a closet under a 400w HPS. They are currently 4 days into flower, and were grown outdoors in the vegetative stage. There is mylar on each side of the walls, and a fan blowing from the floor up on to the plants. The temperate on the thermometer is at 100d F, give or take a small amount. I would like to reduce the temperate to about 85d F, but I cant put holes in any walls ruling out using an extractor or something like that. I have the cupboard door open about half Rating: 5