HP kit is also fairly tough.
We had a "computer room" (old office on the top floor, south facing, floor to ceiling windows and no AC). The first thing I did when I got there was recommend AC, the price was too high and the CEO told me that they had never had any problems. I also suggested putting the servers in the cellar, but that was nixed as the mirrored SQL server was down there...
I put a thermometer in the middle of the rack. In the summer, we were getting temperatures in excess of 60°C and most of the kit kept running. I think the highest temperature I saw was around 68°C, the room temperature was over 40°C most days. The first person into the office opened the windows to allow some fresh air in.
One of the servers crapped out, a 7 year old HP ProLiant server, it was so full of black dust that the fans had to work overtime in the winter... I did manage to get budget after that to get a man with a compressor in and we blew out the dust from all of the servers in the rack. They ran reliably after that, despite 60+°C temperatures. I left shortly thereafter, my successor did manage to get the replacement CEO to re-locate the servers to the cellar.