I use a waterproof salomon cap with a columbia ear-warmer in winter. If I need more warmth, my mid layer has a hood.

In summer I use an all-mesh cap designed for runners (Vaga hats) or a Dekine surf-hat if I really need to keep the sun off. The surf-hat is great. Light, packable, breathable, adjustable incase its windy, it floats and the brim is decently wide. It's kinda like a boonie but way better.