A couple of other options. Get a jacket (Gore Passion Plus for instance) that had detachable sleeves. If it gets warmer as the ride wears on, you can at least take your sleeves off and stuff them in the back pocket of a jersey or the jacket itself. The Passion and Passion Plus jacket also can be folded into its own back pocket and then attached to the top tube. They're not cheap, but they are very versatile.
I've also seen people roll their jackets up into a bundle, secured by a rubber band, and then stuff it into one of their water bottle cages. This only works if you have two cages so that you can keep water in the other one.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher