We had 39 C (102F) the other day, almost unheard of here. Dug the portable air conditioner for the house out of storage, hadn't needed it for 2 or 3 years. Plugged it in and nothing, opened it up and found mice had destroyed the wiring. Had to make a run to town for a replacement. The machine shop was at 18C (64 F) at the beginning of the heat wave, its climbed up to 20 C (68 F). It has 8 inch thick walls, insulation in the ceiling below the cabinet shop and well shaded with big trees. Been spending a lot of time out there these days.
Our "lower level" AKA basement houses our living room and my shop. Outside it's 89º, with the heat index it's 100º. our living room is 75º, quite comfortable. Upstairs, where my wife is reading right now, the AC is set at 81º, she often wears a shawl while reading. I can just barely stand it up there.