Cold weather riding is great. And it's all about having the right gear. I ride to work throughout the winter, and the only thing that shuts me down is snow on the trail By right gear I mean:
a) basic "wicking" layer;
b) a thermal layer (fleece)
c) a shell - keeps the wind out, and keeps the heat in.
Ok, that's to keep your core warm. the you have...
Wind resistant biking pants (try at Hudson Trail Fitters or similar outdoor store), underneath this you have fleece layer and normal biking pants. I can do without the fleece layer, however, b/c I'm using really good "Windstopper" biking pants over regular biking shorts. Below 30 degrees, I'll add in the the fleece layer.
Now your extrememties:
a) EXCELLENT winter gloves (wind resistant, great thermal layer) are essential Game over if you don't have these....and prepare to drop $60 to get a proper pair. Or more.
b) Serious, tight fitting thermal hat to keep your head warm. Must have a very dense weave, and keep the wind out. (Again, REI, Hudson TraiFitter or any decent out door store will have these).
c) A neoprene face mask. Seriously. Get one or your face will freeze.
d) Super socks...normal biking socks on first, then big thermal socks over them.
d) Neoprene booties to go over your biking shoes for the absurdly cold days (i rarely use them in Washington DC, but useful every now and then)
So WHY do all this?
a) You can bike year round.
b) You TOTALLY will get bragging rights at the office if you pull this off.
c) You wont have a huge down seasons during the winter;
d) IF FEELS GREAT AND IS A RIOT AND YOU WILL BE PERFECTLY WARM!!!
"D" is the most important part. IT's FUN! And you WILL be perfectly warm and comfortable.
There you have my pitch.:-)