Water is a particularly important thing to remember in winter. Often, when you’re out in colder weather, you won’t feel as thirsty has you would on a warm day, but your body still requires hydration. On milder winter days, an insulated water bottle is sufficient to prevent your water from freezing. If, on the other hand, you plan to hike for a prolonged period in temperatures that are well below freezing, you’ll need to take some additional precautions. Instead of an insulated bottle, use an external insulated sleeve, like Nalgene’s along with an uninsulated, stainless water bottle like the Kleen Kanteen Classic. In the event that your water freezes, you can simply heat up the water directly in the bottle and then slip it back into its sleeve. Heating an insulated water bottle can damage the container.