Move the Ceremony
First, don’t panic. Yes, it is raining on your wedding day, but that does not mean that your entire day has to be a washout. There are still plenty of things that you can do to make the most of this situation.
One option is to move the ceremony inside. If you have a backup plan for an indoor ceremony, great! If not, don’t worry, there are plenty of other options. You can always move the ceremony to a nearby church or even rent out a hall or banquet room (though that’s not ideal, remember this is your wedding day so you can do whatever you want!).