A snack of nuts, seeds, dried fruits, candy bars, or cookies can help maintain body temperature. A thermos with a good hot drink can warm your insides. However, in subzero temperatures it can create foggy windows or even your own little snowstorm inside your vehicle. Extremities Take good care of your body's extremities. Wrists, hands, and ankles are bony and have blood vessels close to the surface, which allows the blood to be cooled if you are not properly protected.
Wind goes right through even the best of knitted wool gloves.
Gloves are most effective if they are windproof and waterproof and have cuffs or Velcro fasteners to keep wind and snow from cooling your wrists and hands. There are numerous glove liners on the market. Several of the knitted stretchy type are comfortable and can be worn in fall and spring without a heavier glove over them. Remember that you're going to have to focus your binoculars, so try all layers on to see if you can still move your fingers easily. Waterproof, insulated boots keep your feet warm and dry.