Strange question I guess, but if you're looking ahead at the weather forecast and it looks like it may rain on your upcoming wedding day, do you always try and find an indoor shoot location just in case, or do you just go with the flow and have umbrellas available for wedding party/bride and groom shots? Indoor locations are mega lame here!
Try to find a nice indoor place. This past year, we got rained in a couple of times. One was a wedding at a prestigious golf club in Virginia. I had scoped the landscape and had all these ideas. Then a monster thunderstorm hit and we were restricted to the event building itself. Just do what you can. A lot of it depends on the couple also. Some couple's will be willing to go out with an umbrella. Some couples are more particular about getting wet and will want to stay in. Ask the bride.
Sam - I would be all over that. Just don't know about the these particular clients I will have a bunch of black umbrellas in the car ready to go though!
Get really great at seeing light and not seeing locations and it won't matter what the weather does. When it rains either work with it outside or head inside and use that awesome, softened window light that you'll no doubt have. It doesn't matter what the location looks like inside, it matters what the light makes it look like. When it rains I shoot in back hallways, vacant conference rooms, hallways, anyplace with shelter and a window. Look at the great images that have already been posted - all about light and location doesn't matter.
I will have a bunch of black umbrellas in the car ready to go though!
and you can water proof your receiver whether it be pw or something else by putting it in a bag or something.