The problem with being outdoors is that the heat can cause sweating and loss of fluids. The problem with vomiting and diarrhea is they remove water from your system. When we are dehydrated, chemical balances in the body change which can cause problems with heart rates and breathing. Like the mucus buildup gets thicker and expels slower from the body. Even A/C can cause a room to be too DEhumidified and our body always needs hydration.
Fluids in the body is like gasoline in a car. Many do not drink enough water. You'll know when enough is too much.
MY Solution: Stay Hydrated.

Getting sick from the heat doesn't have anything to do with COPD. Excessive heat can make breathing a lot harder than usual, and getting overheated can make you sick to your stomach. Getting overheated is no fun for anyone, and if you have COPD, it can be very difficult to breathe normally. I suggest you stay indoors in the A/C.