There's a link in my signature for dealing with heat issues. (if soil is your medium)
Keep in mind I'm home all day, and monitor the temps and my meds very carefully. Results may vary, but the plants are pretty resilient. If you are not there to monitor changes, likely you should aim for lower temperatures.

After you get the hang of it, you get used to walking into a 98 degree flower shed, and thanking god that the temps are ok. :thumbsup: