Science fiction often depicts humans visiting alien planets which have unbreathable atmospheres. No problem; they are shown wearing atmosphere suits including a helmet with a transparent visor/faceplate or a transparent globe over the entire head. My question is, what happens when it rains? Most of the designs of helmet shown on SF cover art would mean that all the wearer would be able to see in heavy rain is a curtain of water streaming down the surface of the clear polycarbonate plastic or whatever the visor is made of. Our intrepid explorer would then have no option than to stay where he or she was until the weather cleared.
Two strategies immediately occurred to me. One is to have little windscreen wipers. The other is to carry an umbrella. Would these strategies work? Less drastically uncool would be to have a little brim to your helmet, possibly retractable, but with that you are still going to have difficulties if you need to look up.
I also ask this question on behalf of any aliens currently visiting my corner of Earth, where the weather is particularly dismal today.