Cycling in the cold requires special clothing. We will assume you will wear a helmet which will warm your head, however it is not enough when temperatures drop below 40 degrees ( Fahrenheit ). Ones head and ears need extra protection, however a thick hat will not work with a helmet.  A thin hat  is ideal to allow the helmet to fit snugly and keep your head and ears warm. 

Cycling jackets will work fine for temperatures slightly above freezing. Once it gets below freezing riders will need to add layers to stay warm. First make sure to tuck in your shirt to help insulate your upper body. A thin windbreaker underneath the cycling jacket is perfect for temperatures slightly below freezing. For super cold temperatures a third layer is required, keep in mind cycling jackets fit tightly, it is unlikely that one will fit anything more than a windbreaker underneath, Rain jackets are baggy, they are the perfect third layer to fit on top of the other two layers.