I usually wear a waterproof eVent lined jacket and similar pants over my regular clothes and maybe an insulation layer for when it gets really cold (but then I'd probably be walking, riding my regular bike, or driving if it gets bad enough).

For snow/ice, they usually take care of the streets so I think my knobby 4" tires should do great when it comes to snow and salted streets: My biggest concern is salty slush corroding things so I'll have to pay extra attention to wiping everything dry though.