What should I wear...?

So, this is my dress....


We're having an informal outdoor wedding in mid-September on a lake. I imagine it will probably be cooling off early that day and I want to get something to wear to keep me warm after the ceremony. I don't want to change out of my dress...I just want something I can throw over. Any ideas? Keep in mind, it's informal!
Thanks!!!

OK, this is a little expensive, but so pretty. . .
(Princess bride tiaras, $189)


You may able to get a cape, or, one of those shawls you put over your head, but that may cover your dress too much.


If you want a wrap, you could probabaly find one in a department store, for less than the one above.