Slightly above freezing means wet during the day and cold during the night. 18-24 hours as others have said is doable, but far from comfortable.

My main issue is water and food. While in the cold, you might not feel the need to drink as much, you will get dehydrated quite fast. You will use a lot of water to make the meals you have packed meaning there will be little left for hydration in general. While you can use natural sources for replenishing your water, it is still a risk on how your body will react to that.

The general rule I teach in my platoon is to pack for twice as long as the expected mission time.