I have only one example, from the time a scout-leader friend and I took a group of boys for a weekend camping trip. In spite of our pre-trip checklist, many of the boys were unprepared for sleet turning to very cold weather. My buddy and I are gear-heads, so of course we had extra everything. But what saved the day was a roll of super-heavy plastic trash compactor bags. Imagine a group of boys sitting out in the woods with parkas, overboots, "kilts" etc. made out of heavy plastic bags. White bags, at that. Scary! But warm.