I ran a bitcoin mining rig in my garage in Houston, Texas (6x Radeon cards across two workstations) for two years in 2010-2012. No issues, no loss of hardware. Ambient temperature went from 40F to 140F.

Wow those were the early years of mining, must have been quite profitable if you kept the yield for a couple of years till the price skyrocketed.

I sold coins along the way to cover initial investment and then exited the majority of my holding at $500-1500. I sold my final bitcoin in 2017 when prices were sky high. If I had sold everything at peak I would have been extremely wealthy. Maybe next time. :)

That is interesting. Do you know if the Radeon cards throttle automatically when they get too hot? Did you have any custom cooling? I can't imagine they would perform all that great at 140F if they throttles themselves, but them doing so may have kept them functional and error free at the expense of hiding poor performance, unless you have data showing otherwise (and you totally might, it seems like the person setting up that system might also check to ensure it's performing to spec :) )

140F/60C is not really out of band for a GPU, usually throttling starts around 75-80C.

Yes, but they said ambient temperature, and I assumed that to mean the temperature inside the garage (I grew up with a detached garage that was not insulated, it got very hot in the summer, especially when it's over 100F outside, so this doesn't seem outside the realm of possibility to me). It would be significantly harder to disperse heat from the CPU and GPU in that environment.

Open system with a box fan probably has better cooling than a mediocre, closed case. Cursory searching says 105-110F isn't too crazy for a closed case

No custom cooling other than a box fan to move air around inside the garage. Honestly I didn't keep a close eye on them other than making sure they were connected to mining pools.

Ah, well good to know they didn't crash at least. That's better than I would have assumed.