Last year Septemeber, we went to Bayou with my husband. The temps at the time were in the low to 90s with lots of humidity. The tent we had was a 12'x10',7' and the upper panels are not meshed. We had also carried the Frigidaire FFRAO511R1 5,000 BTU Window Air Conditioner just for emergency.
So, we put the AC in the door and a 12'x10' tarp on top of the rainfly and duct taped a couple of survival blankets. I had also read somewhere that keeping one of the windows slightly cracked open at the top prevents condensation from forming inside the tent. Honestly, it didn't work as I anticipated, but it still kept temps in the 76-78 degrees range and around 80 during the afternoons.
I'd say that
running an air conditioner in a tent works and will definitely keep your tent comfortable. It depends on where you'll be camping and a few other factors, but it works.