It was 79F yesterday here. My mining boxes (my most recent has 3x GTX 1660 ti cards in it, single-fan ITX style), @ 80% power limit, were hitting 83-84C on the hottest card.
No A/C, can't run A/C on same circuit as mining rigs, not without shutting half of them down. (Which I also did, shut all but my main rig off from mining, for personal comfort, during the hottest part of the afternoon.)
I do have some fans in a window to bring in fresh air. I'm experimenting today, with one intake and one exhaust. Before, I had both set to intake or both set to exhaust, and had the window in the opposite room open, to get cross-ventilation.