Possible temperature issue

Hey there!
I'm building a cabinet with about 100x100x170cm, but at the moment the only place available for it is in the attic...but my attic during summer gets really hot. I haven't measured it, but surely more than 30ºC.
If this is the case, how can I reduce the temperature inside the cabinet?

Thanks

Use a fan I have my plants in 97f heat or like 33c and all I do it put a tiny ass fan just enough to cause air movement in there growers say to never let it get hotter than like 83 but my shit gets like 97 98 no problem

do you think something like a 12v fan like the ones for cars will do it? or should I use something bigger?

Go to your local computer store get the fan to fit a computer case 12V or wall voltage. Go to your local __ Depot get a dryer kit with the exterior vent just to make it easy. place the fan pulling out; the vent on other side and draw air from the bathroom exhaust fan or the return vent to your central heating some are just flex tubing. Or just get a cheap large computer case it my be cheaper than just the fan. In the attic get it done with duct tape.

Thanks!

Just one more little thing, how many plants do you guys recommend for that space? And I'll be using CFL's, I've read that the recommended is 3000lumens/plant, is this correct?