When a friend & I were touring in Malaysia (the first tropical country I toured in), we had about 1 hour each morning (7am-8am) when it was truly comfortable to ride. We tried to get on the road by 7am and attempted to do as much riding as possible by 11am. If we still had further to go, we'd take a very leisurely lunch break and maybe not start riding again until 3pm when the sun was lower. We found that it was better if we sought out a room with a good ceiling fan but not AC. It made it much easier to go in and out of the room, and to get moving early in the morning. I did the same thing in Sri Lanka and Thailand, though northern Thailand is far enough from the equator that temperatures or much more comfortable from Dec-Feb. I was only riding at altitude in Colombia, so temperatures weren't excessively hot, though I had to deal with lots of (actually, too much) climbing every day and high altitude breathing.