The current big chill is a result of high pressure over the polar region, which has pushed cold air out of the Arctic towards much of northern Europe, parts of Asia and the US. Winds from the north and north east, rather than the south and south west, have brought freezing temperatures to the UK.
Provisional Met Office figures for December show temperatures for much of the UK were 1.5C and 2.5C below the mean temperatures for the last 30 years. Scotland saw temperatures dip still lower - from 2.5C to 3.5C. On Thursday, temperatures in Scotland plunged to -22.3C in places.
Winds from the north also brought cold weather to parts of Asia, with Beijing receiving its heaviest snowfall for nearly 60 years. At the weekend, up to 30cm (12in) of snow fell in China's capital and its neighbouring port city of Tianjin. Dozens of people have also died in a cold snap in northern India.
However, while parts of the world suffer freezing temperatures, the seesaw patterns mean other areas are warmer than usual, including Alaska, northern Canada and the Mediterranean. Met Office figures for the end of 2009 show some places dropped 10C below the average, while others were 10C above.
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