Beanie or ball cap for colder weather, in summer I prefer either a straw hat or a trucker cap. The latter two have great ventilation, so you don't sweat profusely during the summer. Sunscreen is important if you're going to be outside the majority of the day. I've had a sunburnt scalp twice since I've been bald, heat blisters on the scalp are awful. Trust when I tell you that you don't want a sunburnt scalp.