To the OP, no one has yet mentioned that if the purpose of covering your arms is to keep off the sun, the purpose-designed "arm skins" (coupled with s/s jersey) are ideal. There are various priced options available, and they usually come in white, but if you're on a tight budget, Lusso (THE cheap brand) actually make a super-thin lycra arm warmer (in black) that is NOT roubaix/fleece lined, unlike most arm-warmers, so these would keep your arms covered, yet cool, rather than covered and warm.