I'm still not sure why you guys are determined to wear jackets. A summer jacket is still a jacket, and jackets are horrible in this heat. Mesh armor is mesh.

And rather than worry about liquid cooled jackets and vests that you put in your freezer overnight, do what i do and stop every hour or two, pay 1 yuan for a bottle of cold water, drink half of it and pour the the other half over your Tshirt. That cools you right down and keeps you cool as it evaporates.