When the wind blows and the wind chill drops the temp down to -20, yep, it's chilly on the knees. However, my tank is very warm; much more so than trousers. I've been out in the minuses quite a bit and have not had any problems. Good wool hose, a warm coat and gloves and "Bob's yer uncle". The one item I would recommend is a really warm wool toque if the weather is particularly bitter. Keep your head warm and you will loose less heat from your body.