It will rain at some point, of this I am sure. We will not stop for a little rain. If you are prepared, you will be much happier. Get a small, compact umbrellas. You will want to carry it every day.
Rain comes out of nowhere.
Also get a foldable rain poncho. Just bring a cheap one you can throw away at the end of the trip. Pen, Paper and Journal. You will want to remember names, monuments and restaurant addresses for when you return. You may also need to write down your hotel name and address in case you get separated from the group and need to get home.