Like I said, it's best to keep leaf temps no higher than 80. A laser thermometer works great for determining this, and since they're so cheap now I wouldn't want to be without one. Before I fixed some things my grow area was staying under 85, according to a thermometer I hung on the wall. When I got the laser thermometer I found that some parts of the canopy were staying under 80, but some spots were above 90. The only real way to know what's going on is to measure the temp of the leaves in several places.

Now, I have heard of people growing in the attic when the temps reach 105, and they get weed. Can you do it? Yes. Will it produce weed? Yes. Will it produce something close to an optimum yield? No. If that's the only way you can do it though, it is a way to grow some weed.