It is perfectly possible and usually pretty easy to cycle throughout the winter, but you'll need to adapt. In particular, winter can be challenging because it can be wet, cold, slippery, and dark. On the other hand, it's generally easier to dress for cooler temperatures than for extreme heat. Often the biggest problem is avoiding too much clothing; most people dress for the temperature they feel when they get on the bike, but warm up so fast from the exercise that they overheat!

Dealing with water

Dealing with cold

Dealing with slippery conditions

Dealing with dark

References