For many of us, snow is synonymous with Christmas. Christmas cards, songs and movies all portray a 'white Christmas'. White Christmases were more frequent in the 18th and 19th centuries, even more so before the change of calendar in 1752 which effectively brought Christmas day back by 12 days. Climate change has also brought higher average temperatures over land and sea and this generally reduces the chances of a white Christmas. However, the natural variability of the weather will not stop cold, snowy winters happening in the future.