As the weather becomes more unpredictable, outdoors fans need to put a few more items in their packs, blinds and boat bags to keep the elements at bay, especially in emergencies.

One of the lightest and most inexpensive insurance policies is Adventure Medical Kits Thermo Lite Bivvy Sack ($33). The tapered sack consists of a reflective, nonwoven fabric on the outside and a napped inner layer to wick away dampness. It has a foot vent to let heat escape.

AMK says the waterproof, windproof bivvy sack reflects as much as 80 percent of body heat, making it a perfect add-on to a regular sleeping bag to extend the comfort range or to use alone in summer.

The nylon stuff sack reduces the sack to a package no bigger than a large soup can, and the whole thing weighs a mere 7 ounces.