In Seattle, riding in the Winter means riding in the rain, so there is a lot of overlap between these two topics. This page is about cold, dry days. For tips on enjoying yourself in the soggy stuff, see the Rain Page.
Winter commuting Tips
Warmth 101 - Your degree of warmth will likely depend on your route. Riding on flat ground or uphill, your body heat will amaze you. Coasting downhill in the wind can be deadly chilly. Dress accordingly. It might take a little trial and error, so give yourself time to adjust on your first few attempts.
Winter commuting Gear
Gloves - You can get fancy neoprene cycling gloves for $60 or more, or you can get some cheap fleece gloves (windproof fleece, polar fleece, whatever) for around $5. Synthetic fleece is warm and cozy, stops the wind, and dries quickly if they get wet.
Jacket - I wear one of those bright yellow cycling jackets in the winter. They stop the wind and the rain and you can layer underneath them however you like. Cost: About $80.
Knickers - I love biking in knickers, AKA pedal-pushers. They are the perfect pants for biking. Light and free. Out of the chain and pedals. Very comfortable.
Neck Gaiter - A cheap, fleece neck gaiter (Turtle Fur) will keep that icy air from running right down your collar on the cold winter days. Priceless.
Fleece Vest - On the really cold days, I slip a fleece vest on underneath my jacket. The added core warmth is perfect, without encumbering or overheating your arms. Cost: about $12.
Fleece Ear Warmer (muff) - I don't use one of these because I have a skull cap (see below), but it's a good idea, I see people using them all the time.fleece ear warmer
Pants - In the bitter cold, it's time to cover those legs. Many people wear tights (long spandex). I prefer something looser. You can find some cool outdoor pants in the camping/climbing department of your favorite outdoor store, sometimes called "soft shell" pants. A velcro strap around the cuff and you're good to go. They are breathable, water-resistant and comfortable. Cost: $50 - $100.
Skull Cap - A thin, wicking cap is essential on cold winter days. They sell them to go under your ski or climbing helmet, they are thin and made of synthetic material that dries quickly. I keep one on hand to keep the tips of my ears warm on those really cold days. Cost: about $12.