Just as a side note... I have other panniers than the Ortliebs, but the Ortliebs are some of the best I have had over the years. They are honest to god waterproof. Many years ago I used stitched nylon ones that were of decent quality, but they weren't totally waterproof, I still had to put things in a plastic bag to keep them totally dry.

I have a set of canvas panniers (Basil Karavans) on my city bike that stay on there year round. They are fairly waterproof, but will leak if the rain is heavy enough. That bike doesn't get ridden in the rain that often. Best use I have found for my Ortliebs so far was for a family get together. Packed them full of ice and beer, rode to the gathering. Everyone was suitably impressed.

Aaron