Hah.. I live in Toronto, and I used to cycle year round, but I don't anymore.. I think "too lousy to cycle" is a very subjective thing..

When I was working for a startup I could show up sweaty and grimy (or looking like a Mad Max extra in the winter).

Now I'm in a management position in a larger company, so while I still cycle to work as much as I can, I usually have to bring a change of clothes with me (dress shoes, shirt, etc) so weather (heavy rain or just generally cold/snowy) affects my choice much more now..

I wish I lived somewhere that was a steady 23 degrees year-round. ;-)

I grew up in Southern Ontario and when I was in high school I biked year round. I agree it's pretty rare that it's impossible to bike in the winter, and a good mountain bike should get you through pretty much any weather. The tires are the important part of the equipment.

But it can be downright unpleasant. Dressing right is the hardest part. If you don't do it right, your core will overheat at the same time you get frostbite on your hands. I had to wear ridiculous getups sometimes like touque, tube, heavy gloves, winter boots... and a t-shirt.

I'm close to Ottawa. You can get by if you are riding mostly downtown, but if you're riding a road bike, it gets treacherous elsewhere very quickly. Fatter tires surely help.