January 1985 Arctic outbreak

The Winter 1985 cold wave was a meteorological event, the result of the shifting of the polar vortex further south than is normally seen. Blocked from its normal movement, polar air from the north pushed into nearly every section of the eastern half of the United States and Canada, shattering record lows in a number of areas. The event was preceded by unusually warm weather in the eastern U.S. in December 1984, suggesting that there was a build-up of cold air that was suddenly released from the Arctic, a meteorological event known as a Mobile Polar High, a weather process identified by Professor Marcel Leroux.

From Sunday, January 20, to Tuesday, January 22, 1985, the polar vortex, coupled with a large ridge of high pressure, moved polar air into the United States as far south as Florida. Unlike most cold air systems, a pattern of self-modification did not immediately occur, i.e. seasonable temperatures were absent for a number of days, a rarity in forecasting.

The Arctic air mass started moving into the United States on the evening of January 19 and the morning of January 20. An early victim of the air mass was the city of Chicago, which recorded a record low of −27 °F (−33 °C), coupled with 25 miles per hour (40 km/h) winds to produce a wind chill of −77 °F (−61 °C), also never recorded before. The wind chill calculation was adjusted in 2001, which would make the value about −60 °F (−51 °C) on the new scale.St. Louis saw a low of −18 °F (−28 °C). Pittsburgh woke up that morning to find a low of −18 °F (−28 °C), the coldest morning since 1899. In Cincinnati, the morning temperature of −21 °F (−29 °C) tied for the fourth-lowest minimum temperature in the city's history, outdone by a cold mass the year before and a blizzard in 1977.Cleveland fell to −18 °F (−28 °C), which was at the time a record.Memphis recorded a low of −4 °F (−20 °C), setting a record low for that day. The coldest temperature in the contiguous states on Jan. 21 was −24 °F (−31 °C), in the unlikely locations of Akron, Ohio and Knoxville, Tennessee.

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