Prepare a contingency plan for a rainy day. I don't think you have to avoid outdoor photos altogether (though you might if it's a downpour). How about embracing the rainy weather with the appropriate accessories? I plan to have them on hand, just in case for some fun photos.
The classic trench. If you don't already own one, this might be a good excuse to pick one out.
Rain day shoe attire. You can rock your heels once you're in the Church but these Wellies will keep your feet dry and warm when you're en route. And they'd make for a cute photo op.
A classic black umbrella. Maybe add a white monogram or your new last name.