I wear a boonie hat while working out here in the desert. While it does an excellent job keeping my ears from turnings into pork rinds, the thin fabric resting close to my head does little to prevent the radiant heat from cooking the top of my skull!
I've found that here in the dry side of Hell, a cowboy hat actually works great. It keeps the sun off my ears and doesn't cook my noggin. They also do an excellent job at keeping the rain off.
The problem is that the sturdier, felt hats are really hot in the summer while the cooler, straw hats don't take hard use very well and stand out like a sore thumb amidst the dirt and the brush.
But if I'm going to be stuck out in the sun for hours at a time I usually wear my trusty Resistol.
Good judgment comes from experience. And experience… well, that comes from poor judgment.