2. PREPARATION IS THE KEY
So the rains are in, dark and stormy skies, windy, etc. Don't worry about it.
Grab a few clear brollies a few days before. It'll give you enough time to source some in case the local shop doesn't have any.
Your dress will get wet, make the best of it. If you worry about getting wet, you'll definitely notice it in the photos. It'll make your photographers job just so much harder. Remember you haven't got the power to change the weather.
If your ceremony location is outdoors, have a backup option. Especially if the rain is torrential. Most onsite venues do have backup options, such as Mali Brae Farm.