The semps should all be winter hardy in your location, Pia. My semps were covered by feet of snow some years, and no snow others. Snow cover is better than not, when the temsp drop to zero or thereabouts. Cold, dry winds can be an issue causing them to dry out over winter. If you get frost and occasional snow or rain, but not temps not far below freezing, they will thrive.
As the snow cover melts in the spring, I will find my semps smiling at me as they often are showing signs of growth while still surrounded by snow. They are happy with snow cover.
