Cold Conditions Boot. Reaching more than 10 inches high, this is the warmest boot Muck makes for children, rated at minus 40 degrees. Dry, comfortable and warm with low profile outsole. A great boot to wear hunting with dad, or to play outside on a snowy cold day. Comfort Range: -40°F to 40°F. Warm fleece lining. 5mm CR flex-foam. Self cleaning ribbed outsole.