I keep a few 30 gallon trash bags in my GHB.
In an urban area I don't feel that carrying a tent to be that necessary.
I do have a rain poncho in mine but a few holes in the trash bag for head and arms and that can help keep you dry.
The trash bag could also be used to collect rainwater or to melt snow in.
They could also be used to make a lean-to.
They weigh nothing and take up very little space