If you are a little worried about the weather on your wedding day you can always pre-book The Newmarket Tannery Mall. This is an absolutely incredible place. Decorated in Italian Marble with a three story fountian, the mall closes all the retail stores leaving the cafe and the restuarant open just for Photography every Saturday.
If you are the type of person who would feel more comfortable pre-booking a back-up in case of rain you may do so for a fee of $72.00 including taxes. You will have to fill out a liability form when you book.
Usually, however The Newmarket Tannery Mall is booked in the event of rain and done so on the day of the event. I have shot there over 100 times and have never had a problem getting a spot - if you are worried then pre-book, if not book where you would like and if it does rain then you may pay on the spot $107.00. Again you will have to fill out a liability form when you arrive.