Months With More Extremes and Outliers Than Others

[Lettucing Gutted]

Whilst all the months of the year have historically given us both remarkable cold and warm CETs looking at http://www.metoffice.gov.uk/hadobs/hadcet/mly_cet_mean_sort.txt I have noticed that some have greater ranges between the coldest and warmest record CETs than others.  The winter months (especially January) have the biggest differences between record cold and warm months whilst the late spring though early autumn period (especially July, August and September) has the smallest difference between record cold and warm months.

 

Here is the list of months in order of difference between their record cold and warm months:-

 

1 January 10.6c 2 February 9.8c 3 December 8.9c 4 March 8.2c 5 October 8.0c 6 November 7.8c 7 April 7.1c 8 June 6.7c 9 May 6.6c

10 July, August and September 6.3c

 

The gap of 0.7c between the top 4th (1740 -2.8c) and 5th (1963 -2.1c) coldest Januaries suggests that the top 4 cold Januaries have slightly exaggerated the difference for January with 1795 (-3.1c), 1684 (-3.0c), 1814 (-2.9c) and 1740 (-2.8c) being very cold outliers.

 

The gap of 0.5c between the top 4th (1740 -1.6c) and 5th (1986 -1.1c) coldest Februaries combined with the gap of 0.4c between the top 1st (1779 7.9c) and 2nd (1869 7.5c) warmest Februaries suggests that the top 4 cold Februaries and the top 1st warm February have slightly exaggerated the difference for February with 1947 (-1.9c), 1895 (-1.8c), 1855 (-1.7c) and 1740 (-1.6c) being very cold outliers and 1779 (7.9c) being a very warm outlier.

 

The gap of 0.6c between the top 2nd (1785 1.2c) and 3rd (1748 1.8c) coldest Marches combined with the gap of 0.7c between the top 2nd (1938 9.1c) and 3rd (1997 8.4c) warmest Marches suggests that the top 2 cold Marches and the top 2 warm Marches have slightly exaggerated the difference for March with 1674 (1.0c) and 1785 (1.2c) being very cold outliers and 1938 (9.1c) and 1957 (9.2c) being very warm outliers.  The CET record difference for March has also been exaggerated by the erratic 20th and 21st Century Warming Trend which has given us the top 4 warmest Marches which are 1948, 1990 and 2012 (all 8.3c), 1997 (8.4c), 1938 (9.1c) and 1957 (9.2c).  In complete contrast to this the very warm March 2012 was followed only a year later by the joint 9th coldest March 2013 (2.7c) which is the coldest month of the whole January 2011 though August 2014 period!  March 2013 is even colder than every December in between 1995 and 2010, every January in between 1997 and 2010 and every February post 1996!

 

The gap of 0.5c between the top 1st (1701 and 1837 4.7c) and 2nd (1782 and 1809 5.2c) coldest Aprils combined with the gap of 0.6c between the top 2nd (2007 11.2c) and 3rd (1865 10.6c) warmest Aprils suggests that the top 1 cold Aprils and the top 2 warm Aprils have highly exaggerated the difference for April with 1701 and 1837 (both 4.7c) being very cold outliers and 2007 (11.2c) and 2011 (11.8c) being very warm outliers given to us by the erratic 20th and 21st Century Warming Trend.

 

The gap of 1.2c between the top 1st (1833 15.1c) and 2nd (1848 13.9c) warmest Mays suggests that the top 1 warm May has highly exaggerated the difference for May with 1833 (15.1c) being a very warm outlier.

 

The gap of 0.7c between the top 2nd (1676 18.0c) and 3rd (1826 17.3c) warmest June suggests that the top 2 warm Junes have slightly exaggerated the difference for June with 1676 (18.0c) and 1846 (18.2c) being very warm outliers.  Funnily enough the 2nd warmest June occurred only a year after the coldest June on record in 1675 (11.5c)!

 

The gap of 0.7c between the top 2nd (1983 19.5c) and 3rd (1783 18.8c) warmest Julys suggests that the top 2 warm Julys have slightly exaggerated the difference for July with 1983 (19.5c) and 2006 (19.7c) being very warm outliers given to us by the erratic 20th and 21st Century Warming Trend.

 

The CET record difference for August has been highly exaggerated by the erratic 20th and 21st Century Warming Trend which has given us the top 4 warmest Augusts which are 1947 (18.6c), 1975 (18.7c), 1997 (18.9c) and 1995 (19.2c).  Funnily enough the coldest August on record in 1912 (12.9c) occurred only a year after the 6th warmest August in 1911 (18.2c)!

 

The coldest September on record of 10.5c is shared by 4 years (1674,1675, 1694 and 1807) with the first 2 being consecutive!  No other month of the year has this accolade!  In complete contrast to this the warmest September on record 2006 (16.8c) is the warmest month of the whole August 2006 through June 2010 period!  September 2006 is even warmer than every June post 1976, every July in between 2006 and 2010 and every August in between 2004 and 2013!

 

The gap of 1.1c between the top 1st (1740 5.3c!) and 2nd (1817 6.4c) coldest Octobers combined with the gap of 0.4c between the top 3rd (1683 and 1692 6.5c) and 4th (1896 6.9c) coldest Octobers suggests that the top 3 cold Octobers combined with the erratic 20th and 21st Century Warming Trend has highly exaggerated the difference for October with 1740 (5.3c!), 1817 (6.4c), 1683 and 1692 (both 6.5c) being very cold outliers.  The erratic 20th and 21st Century Warming Trend which has given us the top 5 warmest Octobers which are 1921 (12.8c), 1995 (12.9c), 1969 and 2006 (both 13.0c), 2005 (13.1c) and 2001 (13.3c).

 

The gap of 0.5c between the top 1st (1782 2.3c) and 2nd (1915 2.8c) coldest Novembers combined with the gap of 0.5c between the top 1st (1994 10.1c) and 2nd (2011 9.6c) warmest Novembers suggests that the top 1 cold November and the top 1 warm November have highly exaggerated the difference for November with 1782 (2.3c) being a very cold outlier and 1994 (10.1c) being a very warm outlier.  The top warmest Novembers 2011 (9.6c) and 1994 (10.1c) have also been given to us by the erratic 20th and 21st Century Warming Trend.  The joint 7th coldest November 1919 (3.3c) is the coldest month of the whole March 1919 though October 1923 period! November 1919 is even colder than every December in between 1917 and 1925, every January in between 1919 and 1929, every February in between 1919 and 1924 and every March in between 1917 and 1955!  In complete contrast to this the joint 11th warmest November 1978 (8.5c) was followed by the 19th coldest winter 1978-1979 (1.57c) whilst the joint 9th warmest November 2009 (8.7c) was followed by the joint 35th coldest winter 2009-2010 (2.43c)!

 

The gap of 0.5c between the top 5th (1874 -0.2c) and 6th (1784 and 1981 0.3c) coldest Decembers combined with the gap of 0.4c between the top 1st (1934 and 1974 8.1c!) and 2nd (1852 7.7c) warmest Decembers suggests that the top 5 cold Decembers and the top 1 warm Decembers have slightly exaggerated the difference for December with 1890 (-0.8c), 2010 (-0.7c), 1676 (-0.5c), 1788, 1796 and 1878 (-0.3c) and 1874 (-0.2c) being very cold outliers and 1934 and 1974 (both 8.1c!) being very warm outliers given to us by the erratic 20th and 21st Century Warming Trend.  The 2nd coldest December on record 2010 (-0.7c) was not just colder than every December after 1890 but it was even colder than every January after 1979 and every February after 1986!  In complete contrast to this December 2010 was followed by the 2nd warmest year on record 2011 (10.70c! just 5 years after 2006's 10.82c!), the warmest spring on record 2011 (10.23c), the warmest April on record 2011 (11.8c! only 4 years after 2007's 11.2c!), the warmest late winter though late spring period on record (February though May 2011 9.28c), the 2nd warmest autumn on record 2011 (12.43c! just 5 years after 2006's 12.63c!) and the 2nd warmest November on record 2011 (9.6c)!

 

January and October seem to have some cold outliers but no warm outliers.  February, March, April, November and December have both cold and warm outliers.  May, June and July seem to have warm outliers but no cold outliers.  August and September seem to have neither warm or cold outliers.

Edited September 2, 2014 by Craig Evans

[Summer of 95]

December has had a bigger range since 2000 than several months have since 16-something.

August and September, and probably July, having small ranges is not surprising given the warm seas and usual lack of cold air sources in late summer and early autumn. However I am surprised April and May are so far down the list, given the variety of weather they can produce. I'm sure it is possible to get an April below 3C or above 13C, if the right conditions persist all month (remember the first half of April 2013, it was barely warmer than March).

November 1994 really was exceptional for the way extreme mildness persisted all month and into December, not even having any spells of average conditions.

Edited August 27, 2014 by Summer of 95