Dan in Brandon thought he would get up and check the birds today so hopefully I will have some information for you all shortly. I'm not too worried though, the birds will keep the snow off the eggs and the adults will be fine. Better now than when they have chicks as they are so much more vulnerable to weather events - snow, cold or wet. And despite (or perhaps because of) the box's location in Brandon, they have been wonderfully protected from all sorts of weather, including tornadoes.
Will post an update as soon as I hear anything.