Christmas Day 1956 was a white Christmas in a number of places. Pressure was high over Scandinavia and this allowed a cold airmass to flow across the UK. Further west, a frontal system engaged the colder air and the preciptation fell as sleet and snow. The heaviest falls were around the Midlands and Northern Ireland, the further east you went, the less snow that fell.
There were very few cold spells during the winter of 1956-57 and it was a very mild winter with a CET of 5.5, milder than any winter since 1997-98.
The cold Christmas spell was short-lived and it became milder into the New Year. The 4th and 5th of January 1957 were especially mild days.
December 1956: 5.7 (+1.2)
January 1957: 5.5 (+1.6)
February 1957: 5.3 (+1.1)