Covered almost entirely by an ice sheet, Greenland summers afford residents the opportunity to enjoy a little bit of sun and some warmer temperatures, reaching the upper 60s. The summer months are the most obvious time to tour the island. While the sudden chill makes wearing a jacket in summer a necessity, residents are able to get outside and enjoy the nice weather. Winter brings another picture – a colder one – with temperatures dropping to -20°F in the north and routinely lingering around 5°F in the south. Up north, in the Arctic Circle, the sun disappears altogether for a time during winter. The weather in Greenland can be extremely unpredictable given the different topography of the area. Low pressures from the southwest combined with high polar pressures in the northeast make for instable conditions that can change suddenly. If you are taking a Greenland trip, be sure to be adequately prepared for all types of weather. Trekkers especially should never set out without proper communications equipment; a sunny afternoon can quickly turn into a brilliant blizzard.