How long you going to be riding? I wouldn't have that much skin exposed to the sun, even in hot weather and I do ride when temps are in excess of 100°F.
I don't like the feel of globbing sunscreen all over me, so I rely on snug fitting cycling jersey's and shorts that come to my knees along with sun sleeves. The cycling clothes I see for sale all boast a pretty high SPF.
Of course it's hotter when I have to stop for period of time. However in hot weather I try to ride places I can keep 16 mph or better so the evaporation keeps me cool. I try to keep hills that slow me down to 10 mph off my routes when it really hot.