is one of the world's most northerly settlements and is both the largest city built on permafrost and the largest city inside the Arctic Circle. Norilsk has an extremely harsh subarctic climate (according to the Köppen climate classification, it is between subarctic (Dfc) to tundra (ET)). It is one of the coldest cities in the world – far colder than Murmansk, which is located at almost the same latitude. As a result of Norilsk's geographical isolation on the Taimyr Peninsula, the rest of Russia is usually referred to as “the mainland”, and expressions like “move to the mainland” or “on the mainland” are common among locals. Climate Despite being located inside the Arctic Circle, Norilsk has a subarctic climate (Köppen climate classification Dfc) with very long, extremely cold winters (from early October to May) and very short, mild summers. Norilsk experiences negative temperatures for about 240 days a year, and snow cover lasts from seven to nine months, with more than 50 days of snowstorms. Strong winds are common. The average temperature in January is about -27 °C. The midnight sun is above the horizon from May 20 to July 24, and the time when the sun does not rise, polar night, lasts from approximately November 30 to January 13. Summer is short (mid-July) and cool, with an average July high of +14.3°C, though temperatures can sometimes rise above . Norilsk has an average annual air temperature of −9.6 °C, with an annual variation of absolute temperatures of 85 °C. The average annual relative humidity is about 76%. Much of the surrounding area is naturally treeless tundra, and there are very few trees in the city itself. Norilsk-Talnakh nickel deposits The nickel deposits of Norilsk-Talnakh are the largest-known nickel-copper-palladium deposits in the world. The deposit was formed 250 million years ago during the eruption of the Siberian Traps igneous province (STIP). The STIP erupted over one million cubic kilometers of lava, a large portion of it through a series of flat-lying lava conduits below Norilsk and the Talnakh Mountains. The current resource known for these mineralized intrusion exceeds 1.8 billion tons. Norilsk is a center of non-ferrous metallurgy and is home to mining giant Norilsk Nickel's mining operations. The smelting of the nickel ore is directly responsible for severe pollution, which generally takes the form of acid rain and smog. By some estimates, Norilsk's nickel mines produce 1 percent of