some answers are more helpful than others........
if vis deteriorates, you may wish to configure accordingly - turning your landing light on might alert other aircraft to your presence
if rain is also a bit sleety, and depending upon how your plane is aspirated, you may wish to apply carb heat
if you've been a bit higher up for while where it's properly cold, and you've descended but your plane's still cold soaked, then avoid the rain. If you can't avoid the rain, then watch for ice on the wings and learn where the demist controls are inside the cockpit
as for the windscreen wipers, you'll find the prop wash does a good job of keeping the screen clear