A light weight tarp has proven very handy over the years during wet weather on bike and kayak tours. I do not like to be tent bound due to weather. My current sil-nylon tarp from Campmor weighs 12 oz @8x10 foot size. The whole package of pole, line and stakes weighs just over 16oz. Total cost around $65. I can cover a picnic table, bike and/or even a fire pit [carefully] to keep the rain out. I precut the line for each tarp grommet at home for a standard setup of the tarp and practice the setup a bit so there are no surprises on the road.

There are more expensive SUL tarps that weigh under 8oz made of cuben or spinntex material from sailboat sails that are very strong and with a catenary cut in the design spill wind well. [$150+]