I wear a -33 brand mid-weight merino wool t-shirt, white to reflect light and heat. If it gets really warm I just soak it in the lake, wring it out and put it back on- much more comfortable wet/damp than cotton or synthetics. If you get sweated up on the portage it dries quickly as well. At the end of the day, rinse in the lake and hang to dry. Also a very wide brimmed off white hat that can also be dunked for extra cooling. Stop for quick swims. Wear shorts. Sleep with the fly off, clips connected at the head and foot of the tent- fly bunched along it's length, if I wake to rain coming through the mesh it's just a matter of seconds to shelter the sleep chamber.