The tradition of white Christmases probably owes more to Charles Dickens than it does to anyone or anything else. At no period in the last 250 years has the Christmas holiday been a particularly snowy one, and those familiar Christmas card snow scenes are very much the exception rather than the rule.
We can extend the generalisation to December as a whole. Most of the severest winters in history did their worst during January and February, and occasionally even March. Snowy Decembers are rare: there were just two during the twentieth century, in 1950 and 1981. Over lowland Britain there is an average of just two days per month with snow falling, and three days per month with snow covering the ground. Much more often December appears to be a late-autumn month, characterised by frequent rain and gales, occasional brief colder interludes with fog and frost, and distinguishable from November only by the shortness of daylight. Once upon a time December was an even darker and gloomier month than it is now, but the clean air legislation of the 1950s and 1960s resulted in a marked improvement in the sunshine records of all our towns and cities.
The following table shows the decade-by-decade changes in temperature, rainfall, sunshine, and thunderstorm frequency since 1890, which enables us to place recent fluctuations in December weather into some sort of historical context:
| Decade | Mean Temperature | Rainfall | Sunshine | Snow Falling | ||||||||||||||||||||||||||||||||||||||||||||||||||
| 1890-99 | 3.7°C | 89mm (3.51in) | 54 hours | 0.7 days | 1900-09 | 4.3°C | 93mm (3.66in) | 56 hours | 1.3 days | 1910-19 | 5.1°C | 127mm (5.00in) | 65 hours | 2.5 days | 1920-29 | 4.5°C | 98mm (3.86in) | 63 hours | 1.5 days | 1930-39 | 4.4°C | 85mm (3.35in) | 50 hours | 0.3 days | 1940-49 | 4.8°C | 83mm (3.27in) | 54 hours | 1.1 days | 1950-59 | 4.9°C | 95mm (3.74in) | 52 hours | 1.1 days | 1960-69 | 3.5°C | 97mm (3.82in) | 55 hours | 2.5 days | 1970-79 | 5.3°C | 93mm (3.66in) | 73 hours | 1.2 days | 1980-89 | 5.2°C | 99mm (3.90in) | 66 hours | 2.0 days | 1990-99 | 4.6°C | 101mm (3.98in) | 63 hours | 1.4 days | |
December weather since 1890 averaged over England and Wales.
The decadal analysis of December temperature shows the same warming process during the twentieth century that we have seen in the other months of the year, but it has been a very erratic warming. There was a huge jump from a mean temperature from 3.5°C (38.3F) in the 1960s to 5.3°C (41.5F) in the 1970s, followed by a slight easing back since then.
There is no obvious trend in rainfall with most decades averaging between 90 and 100 millimetres. However, the 1910s stand out as an exceptionally wet decade, averaging 127mm, while the 1930s and 1940s were relatively dry at 84mm.
Sunshine average 60 hours over the whole century, but there has been a marked improvement from just 50 hours in the 1930s to 73 hours in the 1970s, followed by a slight easing back during the last 20 years.
An examination of the snowfall statistics shows that the frequency of snow falling appears to be quite independent of mean monthly temperature. This paradox may be explained when one considers that the majority of cold Decembers were also dry, whereas fleeting snowfalls can occur even during the mildest of months. The Decembers of the 1930s were almost entirely snow-free, while the snowiest decades were the 1910s (the third warmest) and the 1960s (the coldest). In 53 of the last 100 Decembers there was no day with a general snow-cover, while in 1950 there were 17 such days and in 1981 there were 22.
© Philip Eden