I'm assuming you're working from a tripod and photographing landscape-type subject matter. At least with telephotos, lens hoods will help as long as it's not really driving rain or snow. The hoods for many WA's are not deep enough.
For those of us who don't have a camera assistant like Lisa , shielding the front of the lens with a hat, glove or other cover until the moment you shoot will often work. In between shots, wipe off the front element or filter and cover again.