Thanks for all the input, guys. It was running at 39C when I got home this evening, so I just disconnected the 4" dryer vent; pointed a house fan toward its intake; and left the door open to that room...

I might have to just turn it off before I leave for work tomorrow since the heat knocked it down to almost 2THs during the hottest part of today... Back up to ~3.5 once I got the cooling under control. This'll be an interesting first Summer of mining.