Below is what I do for my soil grow during our hot summer months in the southwestern desert. I have never grown hydro, so am unable to verify any of this for anything other than soil grows.
My flowershed is an outdoor shed approx 8' x 12' x 8' tall, of which a quarter if it is for growing. (no, it's not a metal shed)

In my humble (sometimes) opinion, "must keep temps below 80" is a guideline, especially appropriate for beginners.
-However-
Being anal about it is truly unnecessary. Ambient temps inside my outdoor growshed (2 x 400w HPS's) often reach the low 100's. This is including having the window A/C unit on 'high'.
Does it slow the growth...? Yes, a tad. Delays harvest about a week or so. However the yield is there and the quality is there.

First technique I learned
...quit hanging the thermometer by the canopy top. Was too depressing and stressful. All of my temps listed are ambient room temp, taken from the side of the grow, about 5' off the ground. I use the 'back of the hand' method of determining canopy temps. If it's not too hot for me after a minute or so, they'll be fine. (change hands often when doing this, or go around with one hand tanned, one hand not tanned)

Window A/C units.
When using a crappy window unit A/C, and it's real hot...open a vent or window, just a crack. (the higher the vent, the better) Trapped, heated air doesn't cool very well.

Never overfeed when hot.
...don't feed full-strength nutes all at once. Split it up into a couple of 'light' feedings equaling the same nute intake per week as recommended by manufacturer. Example...Instead of giving once-weekly nutes at 2 tsp per gallon, give 2 feedings at 1 tsp per gallon. (I give mine on mondays and thursdays) On the other days, I add either plain ph'd water, or micronutes, per my schedule. (Fox Farms) The strongest additive I put in the potting soil prior to use is worm castings and michorrizae fungi. I steer-clear of manures. (not so during the winter months)

Never spray with the lights on. Each drop of water sitting on the leaf acts just like a magnifying glass, and it will burn the leaf tissue. Flowering ladies prefer the lower humidity anyway. Spraying will also increase possibility of mold. You'd be amazed how long a drop of water can remain sandwiched between two leaves. Be careful watering on hot-muggy days, as it will increase your humidity levels, which can also increase chances of mold.

Ditch the intake fans unless it's hooked-up to an A/c unit.
You can add all the intake fans you want to add, and they will never work like having a strong exhaust, placed high to remove nothing but the hot air and cannabis scent. The suction caused by having the exhaust on, pulls-in the exact same quantity of air that's going out. (physics - nature abhors a vaccuum)

Stagnant air traps heat and provides no fresh oxygen or CO2.
I usually have two dedicated 'oscillating budfans' which I keep on 24/7. One on either corner of the front of the grow. Both are pointing at a slight up-angle, but one is only for the space between lamp and canopy, the other blows 'thru' the plants, providing fresh air to soil, and removing any stagnant heat. Obstructions (unnecessary shit in the room) can and will trap heat.

Lamps and plexiglass.
I don't have a cool tube set-up, but when it's just too hot at canopy top, I do hang a 3/8" plexiglass sheet horizontally above the ladies, (just below the lights) to block the direct heat from the lamp.
If nothing else works to keep the temps within 110, I break-down and raise the lights a bit. If it's still over 115, I'll shut the HID's off, and turn on some 23w CFL'S (soft white) to keep the light schedule on target. I don't know if this is a benefit, but it makes me feel better.

This is all I can think of right now, but if y'all have any questions...fell free ask.
Rusty Trichome Reviewed by Rusty Trichome on . Dealing with heat issues in the desert... Below is what I do for my soil grow during our hot summer months in the southwestern desert. I have never grown hydro, so am unable to verify any of this for anything other than soil grows. My flowershed is an outdoor shed approx 8' x 12' x 8' tall, of which a quarter if it is for growing. (no, it's not a metal shed) In my humble (sometimes) opinion, "must keep temps below 80" is a guideline, especially appropriate for beginners. -However- Being anal about it is truly unnecessary. Rating: 5