This region has a subpolar oceanic climate (Köppen climate classification Cfc) with short, cool summers and long, wet, moderately mild winters: the precipitation averages 3,000 mm (118 in) a year in the far west, but precipitation decreases rapidly to the eastern side. Temperatures are steady throughout the year: in Ushuaia they hardly surpass 9 °C (48 °F) in summers and average 0 °C (32 °F) in winters. Snowfall can occur in summer. The cold and wet summers help preserve the ancient glaciers. The southernmost islands possess a sub-antarctic climate typical of tundra that makes the growth of trees impossible. Some areas in the interior have a polar climate. Regions in the world with similar climates to southern Tierra del Fuego are: the Aleutian islands, Iceland, the Alaska Peninsula, the Faroe Islands, Macquarie Island, and the Heard and McDonald Islands.