All the smart ladies here have said all the smart stuff already, but I'll still pitch in with one observation:
my summer shoes are not tight, just as normally snug as they have to be. I have broad feet so my toes are always pushed somewhat together. That makes them a sitting duck once the temperature drops. I have full shoe covers in neoprene that don't really help a lot against cold (but rain and wind, yes) because they're snug too. Even very lightly constricted feet get cold fast. My winter boots are a lot better because they're really roomy and the sole barely flexes at all. When it gets colder I add loose Goretex shoe covers, that cut the wind and create another layer of air. They're a lot thinner than the neoprene ones but work much better. And when it gets really really cold I've folded and taped a layer of newspaper around the toes of the shoes before putting on the shoe covers, works beautifully.
Pre spd pedals and winter boots, I rode several winters with large, worn-out running shoes, medium socks inside and cut-up old thick socks outside, and platform pedals.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett