I've worn both the Exustar & Northwave's in tempatures from about -20C to 10C (-4F to 50F). At around 0C I'd have to switch to thick whool socks. The Exustar would start getting too warm over 5C since they don't breath very well. For the Northwave's I'd have to put on shoe covers over them if it was rainy, slushy, very cold (bellow -10C) or very windy.