Statistical chances for a white Christmas are about 1:10 for England and Wales and about 1:6 for Northern Ireland and Scotland. However, lets have a look at the past years.
1990: A mainly green and mild Christmas Day. Some wintry showers about Scotland and northern England.
1991 and 1992: NIL.
1993: YUP. A reasonable event for most rural areas. Some larger urban areas missed out. However, snow from the southeast to NE Scotland. Best across Northern Ireland. Reasonable over Wales and the Midlands.
1994: NIL.
1995: YUP. A good event for the north. Plenty of snow lying and falling from Yorkshire to Scotland, patchy lying and new snow for Northern Ireland. However, the south missed out again.
1996: NIL. Bookies: YUP. Although some light snow and individual snow grains were observed, snow was not lying in populated areas.
1997 and 1998: NIL
1999: NIL. Bookies: YUP. No real snow by definition. Wintry showers and a mixture of soft hail or sleet. Scotland had some overnight snow later. Only higher grounds in Northern Ireland had a snow cover. All in all very poor.
2000: NIL for much of England, Wales and Northern Ireland. Some light snow or sleet in the West, but no snow cover. Some snow across northern England, especially the Pennines and a reasonable event for Scotland with a significant snow cover.
2001: NIL for the south. However there were snowy rain showers during afternoon. YUP for northern England. NE Scotland had a thin snow cover, snow showers elsewhere. Only Northern Ireland had a true white Christmas.
2002: NIL, NIL, NIL, in fact totally disappointing. Mild with light rains and drizzle. Not even a flake on higher ground.
Most of the info has been taken from Martin Rowleys excellent and comprehensive "Snow at Christmas in the UK" site.
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