structural:summarization
Climate

Ellesmere Island has a tundra climate (Köppen ET) and an ice cap climate (Köppen EF) with the temperature being cold year-round. Two semi-permanent air systems dominate the weather: the high-pressure northern polar vortex and a low-pressure area which forms in different sites between Baffin Bay and the Labrador Sea. Prevailing winds on Ellesmere are northwesterly, cold, and of low humidity due to ice cover over the Arctic Ocean. Seasonal shifts on Ellesmere are sudden and striking: winters are long and harsh, summers short and relatively abundant, with spring and autumn being brief intervals of transition.

Fog regularly occurs near open water in September. While the major air systems strengthen towards their annual peak in winter, the Arctic and Atlantic air masses collide in autumn to produce severe storms at Ellesmere. The storm season peaks in October and persists until the sea freezes. The polar vortex strengthens during the polar night and gives rise to easterly winds which are major hazards for populations, especially given the very low temperatures. January winds have been recorded at 104 km/h (65 mph) with gusts to 130–145 km/h (81–90 mph) at Fort Conger and 65–80 km/h (40–50 mph) at Lake Hazen. Very cold temperatures continue until April and no month passes without experiencing freezing temperatures.

Snowfall begins in late August and does not melt until the June thaw. The seasonal shift in daylight is also extreme. The polar night lasts from four-and-a-half months in the north to about three months in the south.