Things are summer-ish between May and mid-August, when the thermometer busts a gut to climb over 20°C (68°F) on the southwest coast. It can be wet and windy, though, and coastal fog is common. By late August, nights are getting colder and by mid-September, there's new snow and genuinely cold weather. Arctic winters - any time from mid-October to March - are long, harsh and very, very dark. In the far north the sun disappears for months on end, and a perpetual night descends. In the far south, temperatures of -20°C (-4°F) can be expected, but further north it can be -40°C (-40°F) or lower for weeks.