I just watched How I Met Your Mother and while we don't know whose wedding Ted is the best man at we now know that he meets his future bride at a wedding.
Just as Ted and Marshall are making their way inside the church for the ceremony it starts to rain and while no one in the show mentions it, rain on your wedding day is considered good luck. I think it's a good luck omen the same way if a bird poops on you -- people tell you it's good luck to make you feel better.
No matter what the weatherman says I'd pack a few umbrellas in your wedding day emergency kit, especially if your wedding ceremony and reception are at different locations. And while you could just toss any old umbrella in the bag you may want to splurge on a golf umbrella which will cover you and your groom. I've seen some great shots from weddings where the couple is using an umbrella to protect them from the rain. You can even pick up a pattern or color that matches your wedding palette!
You can't tell from the photo above but Dave's brother, the best man, is holding a lavender umbrella over the two of us as it started to drizzle while we were taking pictures outside the temple we were getting married at. Lavender was one of the colors in our wedding palette and the accent color on my wedding dress. My mom found a bunch of lavender umbrellas at a 99-cent store the day before my wedding and bought a bunch of them. We still use them.
Photo Credit: Matthew Septimus/Martha Stewart Weddings