This is not too far OT-- We made this insulated liner to go into one my front panniers. We were riding in +100F weather, and could not keep food or water cool. On a rest day in Cody , Wyo, we went over to Wal Mart and got a blue camp pad and a roll of duct tape. It works well, especially if you can get some ice at a convenience store or gas station during the day. It also keeps cheese from getting too slimy. I've since replaced these panniers, but fabricated a liner for my new ones.

Placing water containers on top of the racks or where they are exposed to the sun makes for good shower water but poor drinking water.