Working at my previous location, we had a 'comm closet' which housed some networking equipment (some stacked cisco 48p switches, and a pair of 6500's used as core networking/outbound traffic stack). This room had a single air vent which jammed cold air into it, which was appropriate for it's original intent as a mop closet (about 2x2m, but wholly insufficient to house networking equipment. As a result it was usually a bit warm inside. The AC kept it under control however, usually 2-7c over ambient outside the door.
I came in to work one day to hear that comm closet absolutely screaming from the fans, and the whole office was very warm (probably around 45c). Turns out the AC in the building died (backups? what's that?) and that room basically turned into a furnace. Now most equipment has nice overheating features, and cisco is no different, but the way theirs worked was there's a 'shutdown threshold' where above that temp it starts a 5 minute shutdown routine unless the temp drops enough. It's at like 95c or something. Funfortunately, if the temp gets too high it seems to basically hard-lock the system which didn't/doesn't shut it down, it just keeps doing *something* with power to the processing units. These two were sitting like giant hair dryers for a few hours not actually processing data.
The room itself was probably closer to 70c ambient, the cladding on all the cat5 in that room (probably 400 runs of it) was soft to the touch (such that I could just pull it off the cable, much of the bulk became partially fused from that event), and I don't even know what the actual 6500's were sitting at, but I'd guess 120c or higher. Opening that door was seriously like opening an oven.
Amazingly, the building switches were still happily switching away. One of the 6500's dumped its config (? don't know why) but it worked fine after letting the damn case cool off and firing it back up, other one was fine after shutting it down for 10m or so then firing it back up. Nothing caught on fire though!