Can’t believe nobody has mentioned using an air puffer bulb to clear the lens. Wiping the lens leads to streaking that can’t be completely resolved until a later date in a dry environment.
The air puffer is commonly used in PRS matches to clear water off the lens. Scope lens (at least decent ones) have a coating that causes water to bead on the lens. The puffer bulb just pushes the water off the lens. If it’s really raining, you aren’t going to keep the lens “dry”, but this method will clear it off long enough to make the shot and not leave it smeared and risk scratching the lens with a dirty cloth or debris already on the lens.
Try it sometime-
https://www.amazon.com/LYECUN-Blaster-Keyboard-Cameras-Cleaning/dp/B0C8HZK7G9