Where can I find air conditioning in Chiang Mai? It's October and I'm dying from the heat

Even at McDonald's, they barely turn on the AC, and the pretty regular cafes are open-air, so they only use fans.
Only Starbucks is cool.
It's so hot I can't even enjoy sightseeing.
What a waste of money.
Where on earth are the cool places... I'm in Old Town.
Do they blast the AC in Nimman Haemin?