You need shelter. You don´t want do carry a lot.
The best solution is to carry a bivy-bag or bivouac-sack. I had one already, but you can also sew one easy. Look at MYOG sites, or try this one: http://www.backpacking-lite.co.uk/diy/make-your-own-bivy-bag.html
Some outdoor-lovers may know a Biwak-Sack or Bivouac-sack for the others... wikipedia :)
condensed water and no good air
And when you have one, you may also have the problem with condensed water inside the sack. As the Sack is an emergency-solution, I don´t want to have a luxurious tent. Because I love to sleep outside under the stars and not in a tent, I just wanted to make my Bivouac-sack a little more comfortable without getting heavy. So it is still an emergency solution and you can make it with just a few more things. It is also flexible, so you can arrange optimally with your given surrounding.
Step 1: The plan
My problem was to get some space between my sleeping-bag and my bivouac-sack. So I want to make it tent-like. I did not want to destroy the fabric, that´s why I realized another solution with clamps. We can keep it simple and flexible.
what we need
You need your walking stick, piece of rope, tent pegs, two different clamps and loops. Putting it all together you have a nice and small sleeping solution and a good shelter.