There's no reason to stop riding in the cold months, I was out yesterday. You just have to dress for the tempature. More layers, winter gloves, shoe covers, and a balaclava are musts. You probably have most of what you need already. Of course rain, snow, ice, etc means workingout inside. But there is nothing nicer than putting in a few miles on a sunny winter day. You'll feel alive, and everybody will think you're nuts! So hit the gym\spin when you need to, ride when you can.
BTW, I was riding yesterday, 29 degrees, just a few miles north of Philly.