I'm with OM. I hike exclusively in shorts (summer and winter), and carry a pair of waterproof-breathable rain pants that double as wind pants or long pants on really cold days (layered over long johns.) If that doesn't work, it's time to go home or do what OM says: hit the sleeping bag.

Many people like long pants with zip-off legs, so they're not carrying a full set of wind pants. I might have to try that some time. (Of course, I also keep threatening to try a hydration system, too. )