Buy a portable AC Unit , They are cheap and easy to move.
Also try to have Fans and also try getting the hot air out and cooler air from outside in.

Definetly plants will still grow in heat , but not optimum.

Good LUck
highallthetime Reviewed by highallthetime on . Is heat really that bad for plants? I started 5 nirvana big bud seeds near the beginning of June, and I'm just getting ready to harvest. I started them outside, and moved them to my attic, where temperatures were over 90 degrees for most of the summer. I planned to flower them all in two rubbermaid storage containers with a 400-watt light, but only one ended up being a female, so she got the whole thing. I had the light on during the night to minimize the daily temperature spike, but I still had no cooling and temperatures Rating: 5