Take a pair of ski gloves and a nice knit wool cap?. 25F/-4C isn't that cold to me. After 20 years of mountain climbing in the western USA, plus trips to Alaska and South America, in temps way below freezing, I've never known anyone who used handwarmers; they're just extra weight. We'd keep warm by using poly clothes that would stay (relatively) dry during the day, and adjusted layers for temperature. When we'd stop at a camp for the day we'd make sure we stayed comfortably warm by adding more clothes layers as the daylight ended so we were always warm. IF you have a sleeping bag make sure you have enough room in it; a lot of the 'ultralight' bags are cut real narrow so that only a person with a 'stick figure' body can properly fit in them without squishing the insulating material (which reduces its ability to retain warmth). also wear some clothes to bed; it always seemed to help vs just relying on a sleeping bag and shirt/shorts. Wear a knit cap while inside your sleeping bag, gloves, and dry socks, along with poly long undies and poly top.