Here in the south, in January and February, we can have snow and ice. Luckily, it usually is gone just as quickly as it comes. But during the day(s) that the roads are bad, people tend to hunker down at home and not venture out. Open houses get canceled as well as broker caravans. If you look at the numbers of homes sold during bad weather, the numbers do drop.
That's here in the south. In colder climates where people are used to extended periods of cold, snow, and ice, I suspect there is a difference. People in the colder areas see their roads opened up much more quickly because of the equipment available to the local governments to clear the snow. In the south, we have less need for this equipment, so we have less of it.
So, if your home is listed for sale and the weather turns nasty, expect showings to drop off a bit. But never fear, as soon as the roads are clear, buyers will be out looking once again!