The coldest winters in Britain from 1900

Winter is defined meteorologically as December, January, and February. For many weather obsessives, a "good winter" is one that is cold and snowy, but for many others cold and snowy winters can be unpleasant or even life-threatening.

Which are the coldest winters of the twentieth century? Here are the top ten (numbers are CET [Central England Temperature series] averages in º Celsius).

1962-63 -0.3

1946-47 1.1

1939-40 1.5

1916-17 1.5

1978-79 1.6

1928-29 1.7

1941-42 2.2

1940-41 2.6

1981-82 2.6

1984-85 2.7

Are winters not as "good" as they used to be? Not lately they haven't, but it isn't clear that there is any trend until very recently (the mid 80s). The Great Freeze of 1962-63 was the third coldest on record. Before this century the coldest winters were 1739-1740 at -0.4 (let down by a relatively mild December) with the coldest being by some way the "Lorna Doone" winter of 1683-84 (average -1.2).

Let's consider the distribution of severe winters, defined by three criteria.

1. Severe months with average temperature less than 2.0C. In the first half of the century, there were 14 severe months, and two occasions (Jan-Feb 1917 and 1929) when there were consecutive severe months. In the second half, there were actually a few more - 17 severe months, with two occasions (1963 and 1979) when there were two consecutive severe months, and only one occasion with three consecutive severe months (1916-1917). This difference however will be statistically insignificant.

2. Very severe months with average temperature beneath freezing. In the first half of the century, there were two very severe months (January 1940 and February 1947. In the second half, there were five (February 1956, January 1963, February 1963, January 1979, and February 1986 - and December 1981 came very close).

3. There have only been four occasions with two consecutive months with mean CET temperatures beneath zero: 1684, 1740, 1878/79, and 1963.

I think two things are happening. First, people's memories are distorted by the exceptionally severe winters of 1947 and 1962-63, in particular. Second, I think there is a recency effect where there haven't been many severe winter episodes in the last few years. Consider this table of the distribution of the number of severe winter months across the decades of the twentieth century:

Older people might be affected by the bump in the middle of the century (particularly the war years, which were exceptional) and compare that with the 90s. There is no overall trend, however: note the scarcity of severe months in the 0s and thirties. It is also possible that central heating means that we are less sensitive to cold weather when it happens.

Here are the severe months (mean less than 2.0 C:

Feb 1902; Dec 1916, Jan 1917, Feb 1917, Feb 1919, Jan 1929, Feb 1929, Dec 1933, Jan 1940, Jan 1941, Jan 1942, Feb 1942, Jan 1945, Feb 1947, Dec 1950, Feb 1955, Feb 1956, Jan 1959, Dec 1962, Jan 1963, Feb 1963, Feb 1968, Feb 1969, Jan 1979, Feb 1979, Dec 1981, Feb 1983, Jan 1985, Feb 1986, Jan 1987, Feb 1991, Jan 2010, Dec 2010.

Here again are the very severe months (mean less than 0C):

January 1940, February 1947, February 1956, January 1963, February 1963, January 1979, February 1986, December 2010.

It is true that although we have some recent hot months, until 2010 you have to go back to February 1991 for a "severe" cold month, and 1986 for a "very severe". This difference is a clear suggestion of change.

Before the twentieth centuries, winters were better (if you like then cold and snowy). Remember the Little Ice Age? In the seventeenth and eighteenth centuries, winter knew how to be winter. Take the coldest winter of them all, the "Lorna Doone" winter of 1683-84, with a CET of -1.2. Or 1739-40, with a CET of -0.4. Now that is chilly.

Cold winters have become less common since the end of the 80s.

We have at last had a cold winter, with 2009-2010 giving an average of 2.4, which would have made it 8th in the above list, and the coldest since 1978-79. January 2010 counts as a "severe" month (at 1.4C).

And of course  December 2010 at last gave us a very severe month, with a CET mean of -0.7, the first such month with a negative CET average since February 1986.

The coldest of all months in recent times remains January 1963 (-2.1C), although January 1814 (-2.9) and some months in the Little Ice age were almost certainly colder, with January 1795 around -3.1C.

I appreciate that not everyone likes cold, snowy winters, and for some they bring misery and ill health.