Dress in layers, avoid cotton!
A big suitcase and a smaller backpack for daytrips. Dress in layers, the temperature and the weather change often on Svalbard. Avoid cotton, use only wool or synthetic. Several layers of wool and windproof outside protection may be required in any season. The windchill may exceed -40°C in winter and early spring. Protect your head and your hands. Special suits, hats, gloves and boots are usually included in the tour's price. As always, bring any medicament you may need. To minimize changes (especially on cold weather) use 36 exposures films and zoom lenses. Bring spare batteries (battery's life is shorter on cold weather). A tripod may be required on darkest months. Overexpose by 1 or 2 stops on white scenes, the snow will be more brighter. Always ask to the tour operator the reccomended gear list, as it always changes depending on the type of the tour and season.
