Personally, I don't like to wear a backpack when I ride because it makes my back sweat.

Wear layers when riding in the cold. If you're not a little cold when you first start riding, then you are probably wearing too many layers.

You can ride in almost any weather or temperature, and studded tires help in the winter.

Some commuters store their clean work clothes at their office, and change when they arrive. You can probably bring work clothes to work on days you don't ride your bike. That doesn't work for me, so I carry everything with me in a pannier that opens up to store a suit. The pannier is big enough to carry my work clothes, laptop, rain gear, repair kit, first aid kit, dress shoes, and more.

Tom