Beyond the calendar -- uncovering the hidden cold months

[Roger J Smith]

Most discussion of cold months assumes that the calendar is the only time frame available. 

However, not every cold interval of that length happens to fall neatly into a calendar month. In the daily records starting in 1772, we can uncover all cold intervals of that length (31 days is used since December, January and March, three of the five months that have contributed a coldest month of any winter half-year period, have 31 days. 

What I discovered was interesting on several levels. 

The average coldest 31-day interval is 0.7 C deg colder than the coldest calendar month. It is not always colder, when February is the coldest calendar month, there needs to be a few equally cold days in late January or early March, otherwise the coldest 31-day interval can be a bit warmer than the cold February. The same is mathematically possible for a cold November but few of them qualified as coldest of the winter season anyway, and those that did usually improved on their low temperature by including a few days or more in December. 

The range of dates that get into coldest 31-day averages extend a little into October and April. The coldest 31 days of 1988-89 started on 29th of October ending on 28th November (4.9 was the average going unbeaten through the mild winter that followed), the only time that any October dates were used. The second earliest start for any coldest 31-day "month" was 1st of November (to 1 Dec) in 1851-52 (any of 1 to 3 Nov 1851 to any of 1 to 3 Dec averaged 3.0, not surpassed at any point later in the winter of 1851-52). This was also the case for 1 Nov to 1 Dec of 1919 (3.3) in the winter of 1919-20. In 1862-63 and 1910-11, the coldest intervals began on 2 Nov and ended 2 Dec (and in both cases were equalled on 3 and 4 Nov to 3 and 4 Dec). 

Three "winters" had dates in April using most of a cold March, and the furthest adventures into April was recent, in 1974-75 (10 or 11 March to 9 or 10 April at 4.0 beat anything from the actual winter) and in 2012-2013, when 9 or 10 March to 8 or 9 April was 2.3 C for the coldest 31 days (it tied 10, 12 or 13 Jan to 9, 10 or 12 Feb 2013 at that value). The only other cold 31-d intervals that used any days in April were in 1868-69 (2 Mar to 1 Apr at 3.7) and 1882-83 (1-31 March and 2 Mar to 1 Apr tied at 1.9). 

In the 248 winters available with daily data, the mean of the coldest calendar month was 2.5 C (before that 1659-1771 it had been 2.1). The coldest 31-d interval averaged 1.8 C so the average "improvement" over the calendar was 0.7 C. This was despite the four cases where the 31-d interval was milder than a cold February by 0.1 or 0.2. There were a handful of cases where the coldest interval was in fact a calendar month, usually January, and that included the coldest month on record, Jan 1795 (-3.1). The coldest 31-d interval turned out to be -3.2 from 1813-14 when 27 or 28 Dec 1813 to 26 or 27 Jan 1814 set that record. 

The coldest 31-d interval does not always use any days from the coldest calendar month. There were a number of cases where the coldest calendar month did not improve much by using data from adjacent months, while some other interval hidden in the data of milder months turned out to be the coldest 31-day interval. That happened frequently enough to make the 0.7 C deg improvement more like 0.8 for the actual months against which the coldest 31-day interval could be compared directly with the months it improved upon. An example from a recent winter -- 2003-04 -- the coldest interval of 3.9 C was from any of 9, 11 to 14 Feb, to 10, 12 to 15 March, and these two months had mean values of 5.4 and 6.5. But the winter improvement was not 1.5, but only 0.9 as Dec 2003 had an average of 4.8. Within that data, the improvement was only slight, to 4.2 for 5 or 6 Dec to 4 or 5 Jan 2004). This kind of offset cold interval was more likely to occur in mild or at least near normal winters, in particular those where perhaps March was the coldest month but a colder interval was shared by two earlier months.

The data for 1772 starting only at 1 Jan seem final given that Nov and Dec of 1771 were quite mild compared to Jan and Feb of that winter (the coldest interval was 0.5 C for 8 Jan to 7 Feb 1772). 

While the average improvement of the coldest month stat was 0.7 C, the extreme value was 2.9 C and three other cases improved by more than 2 C deg. 

In the winter of 1860-61, the months of Dec 1860 and Jan 1861 seem cold enough at 1.5 and 1.7 C, but within that period lurks the equal of such notable calendar months as Jan 1940, with 17 Dec to 16 Jan averaging -1.4 C (2.9 lower than the coldest calendar month). 

The second most prolific hidden cold month in terms of improvement was 2.3 deg, in winter of 1892-93, when 22 Dec 1892 to 21 Jan 1893 managed -0.5 for an average, compared with the 1.8 for Dec 1892 (Jan 1893 warmed to 2.2 overall). 

The winter cold of Jan and Feb 1917 is probably better known already but hidden within that is quite a cold interval of -1.2 C which improves on the 0.9 C average of February by 2.1 deg. (This cold interval runs from 13 Jan to 12 Feb or any of the next four days). That third best improvement is tied by 1866 although in that case the mark was lowered from a rather mild 4.4 to 2.3 in parts of Feb and Mar. 

These are the other 31-d intervals that improved from above to below zero C when compared to calendar months, together with the improvements (sometimes rather slight) of the existing subzero months. Since only 1878-79 and 1962-63 had two calendar months that broke the freezing mark (in the daily data period, there were several earlier), it would not be necessary to add any second qualifiers to the list. The new list ranks the post-1772 intervals uncovered without reference to the ranks of winters from 1659 to 1771, which might have also had some hidden gems we will never know about unless somebody finds some daily data.

In some cases below, the coldest 31-d interval is determined by second decimal and there were other adjacent periods that averaged the same one-decimal value.

 

COMPARING COLDEST CALENDAR MONTHS and 31-DAY INTERVALS

rank_WINTER ___ Coldest cal month ____ Coldest 31-d interval _______ (rank) ___ colder by

01 _ 1794-95 ____ -3.1 Jan 1795 _______ -3.1 _ 1-31 Jan 1795 _________ (2) ____0.0 C deg 

02 _ 1813-14 ____ -2.9 Jan 1814 _______ -3.2 _28 Dec 1813 - 27 Jan 1814 (1) ___ 0.3

03 _ 1962-63 ____ -2.1 Jan 1963 _______ -2.7 _26 Dec 1962 - 25 Jan 1963 (3) ___ 0.6

04 _ 1946-47 ____ -1.9 Feb 1947 _______ -2.3 _26 Jan - 25 Feb 1947 ___ (6) ____ 0.4

05 _ 1894-95 ____ -1.8 Feb 1895 _______ -2.6 _23 Jan - 22 Feb 1895 ___ (4) ____ 0.8

06 _ 1854-55 ____ -1.7 Feb 1855 _______ -2.2 _25 Jan - 24 Feb 1855 ___ (t7) ____0.5

07 _ 1775-76 ____ -1.6 Jan 1776 _______ -1.9 _ 3 Jan - 2 Feb 1881 _____(t9) _____0.3

08t_ 1837-38 ____ -1.5 Jan 1838 _______ -2.5 _ 7 Jan - 6 Feb 1838 _____ (5) ____ 1.0

08t_ 1880-81 ____ -1.5 Jan 1881 _______ -1.7 _30 Dec 1880 - 29 Jan 1881 (t11) __ 0.2

10 _ 1939-40 ____ -1.4 Jan 1940 _______ -1.4 _ 1-31 Jan 1940 _______ (t14) ____ 0.0

11 _ 1985-86 ____ -1.1 Feb 1986 _______ -1.0 _ 1 Feb - 3 Mar 1986 ___ (t20) ____-0.1

12 _ 1779-80 ____ -0.9 Jan 1780 _______ -1.0 _ 8 Jan - 7 Feb 1780 ___ (t20) _____0.1

13 _ 1890-91 ____ -0.8 Dec 1890 _______ -1.9 _ 12 Dec 1890 - 11 Jan 1891 (t9) __ 1.1

14t_ 1878-79 ____ -0.7 Jan 1879 _______ -1.0 _ 12 Dec 1878 - 11 Jan 1879 (t20) __0.3

14t_ 2010-11 ____ -0.7 Dec 2010 _______ -1.5 _ 27 Nov 2010 - 27 Dec 2010 (13) __0.8

16 _ 1783-84 ____ -0.6 Jan 1784 _______ -1.2 _17 Jan - 16 Feb 1784 ___ (t18) ___ 0.6

17 _ 1978-79 ____ -0.4 Jan 1979 _______ -0.5 _ 30 Dec 1978 - 29 Jan 1979 (t25) __0.1

18t_ 1788-89 ____ -0.3 Dec 1788 _______ -1.7 _14 Dec 1788 - 13 Jan 1789 (t11) __1.4

18t_ 1796-97 ____ -0.3 Dec 1796 _______ -0.7 _29 Nov 1796 - 29 Dec 1796 (t23) __0.4

18t_ 1819-20 ____ -0.3 Jan 1820 ________-2.2 _24 Dec 1819 - 23 Jan 1820 (t7) ___1.9

21t_ 1829-30 ____ -0.2 Jan 1830 ________-1.4 _ 7 Jan - 6 Feb 1830 ____ (t14) ___ 1.2

21t_ 1874-75 ____ -0.2 Dec 1874 ________-0.2 _ 1-31 Dec 1874 _______ (t30) ___ 0.0

21t_ 1955-56 ____ -0.2 Feb 1956 ________ 0.0 _ 29 Jan - 28 Feb 1956 __ (t37) ___-0.2

24 _ 1822-23 ____ -0.1 Jan 1823 ________-1.3 _27 Dec 1822 - 26 Jan 1823 (17) __ 1.2

(winters listed had to improve to subzero, some did not, so ranks increase faster than list)

25 _ 1941-42 _____ 0.1 Jan 1942 ________ 0.0 _10 Jan - 9 Feb 1942 _____ (t37) __ 0.1

26t_ 1784-85 _____ 0.3 Dec 1784 _______ -0.1 _12 Feb 1785 - 14 Mar 1785 (t32) __0.4*

26t_ 1828-29 _____ 0.3 Jan 1829 _______ -0.3 _ 5 Jan - 4 Feb 1829 _____ (t27) ___0.6

26t_ 1981-82 _____ 0.3 Dec 1981 _______ -0.3 _ 16 Dec 1981 - 15 Jan 1982 _(t27)_0.6

30t_ 1825-26 _____ 0.4 Jan 1826 _______ -0.1 _27 Dec 1825 - 26 Jan 1826 _(t32) _ 0.5

30t_ 1928-29 _____ 0.4 Feb 1929 _______ -0.1 _ 4 Feb to 6 Mar 1929 ____ (t32) __ 0.5

(unranked below this point as numerous missing cases)

xx _ 1826-27 _____ 0.7 Feb 1827 _______ -0.2 _20 Jan - 19 Feb 1827 ____ (t30) __ 0.9

xx _ 1849-50 _____ 0.7 Jan 1850 _______ -0.1 _23 Dec 1849 - 22 Jan 1850 _ (t32) _0.8

xx _ 1879-80 _____ 0.7 Dec 1879 _______ -0.1 _21 Nov - 21 Dec 1879 ___ (t32) ___0.8

xx _ 1916-17 _____ 0.9 Feb 1917 _______ -1.2 _15 Jan - 14 Feb 1917 ____ (t18) __ 2,1 

xx _ 1840-41 _____ 1.1 Jan 1841 _______ -0.7 _13 Dec 1840 - 12 Jan 1841 _(t23) _ 1.8

xx _ 2009-10 _____ 1.4 Jan 2010 _______ 0.0 _ 15 Dec 2009 - 14 Jan 2010 _ (t37) _1.4

xx _ 1801-02 _____ 1.5 Dec 1801 _______ 0.0 _ 17 Dec 1801 - 16 Jan 1802 _(t37) _ 1.5

xx _ 1798-99 _____ 1.5 Dec 1798 _______ -0.3 _19 Dec 1798 - 18 Jan 1799 (t27) __ 1.8

xx _ 1860-61 _____ 1.5 Dec 1860 _______ -1.4 _17 Dec 1860 - 16 Jan 1861 (t14) __ 2.9

xx _ 1892-93 _____ 1.8 Dec 1892 _______ -0.5 _22 Dec 1892 - 21 Jan 1893 _(t25)__2.3

____________________________________________________________________

* improved by 0.5 over 0.4 Feb 1785, the coldest 31d int assoc with Dec 1784 was 0.0 for 8 Dec - 7 Jan.

_____________________________________________________________________

Recent winters below 1.0 (but not in list above)

xx _ 1984-85 _____ 0.8 Jan 1985 _______ 0.5 _28 Dec 1984 - 27 Jan 1985 _______ 0.3 

xx _ 1986-87 _____ 0.8 Jan 1987 _______ 0.4 _ 3 Jan to 2 Feb 1987 _____________0.4

xx _ 1990-91 _____ 1.5 Feb 1991 _______ 0.3 _ 22 Jan to 21 Feb 1991 __________ 1.2

Since 2012

xx _ 2011-12 _____ 3.8 Jan 2012 ________ 2.1 _ 13 Jan to 12 Feb 2012 __________ 1.7

xx _ 2012-13 _____ 2.7 Mar 2013 ________ 2.3 _ 10 Mar to 9 Apr, also 13/1 - 12/2 __ 0.4

xx _ 2013-14 _____ 5.7 Jan 2014 ________ 5.3 _ mid Jan to mid Feb 2014 ________ 0.4

xx _ 2014-15 _____ 4.0 Jan 2015 ________ 2.8 _ 14 Jan to 13 Feb 2015 __________1.2

xx _ 2015-16 _____ 4.9 Feb 2016 ________ 4.0 _ 9 Feb to 10 Mar 2016 ___________0.9

xx _ 2016-17 _____ 4.0 Jan 2017 ________ 3.6 _ 27 Dec 2016 to 26 Jan 2017 ______0.4

xx _ 2017-18 _____ 2.9 Feb 2018 ________2.4 _ 2 Feb to 4 Mar 2018 ____________ 0.5

xx _ 2018-19 _____ 4.0 Jan 2019 ________ 3.6 _ 3 Jan to 2 Feb 2019 ____________ 0.4

===================================================================================

A few other large drops to near zero averages:

1785-86 _ 0.4 _ 22 Dec 1785 to 21 Jan 1786 (months were 2.8, 2.7, winter coldest was 2.1 March which fell to 1.2 for 20 Feb to 22 Mar).

1799-1800 _ 0.4 _ 12 Dec to 11 Jan (from 1.5 Dec 1799). 

1802-1803 _ 0.1 _ 13 Jan to 12 Feb (from 1.8 Jan 1803).

1853-1854 _ 0.1 _ 15 Dec to 14 Jan (from 1.3 Dec 1853).

1886-1887 _ 0.1 _ 17 Dec to 16 Jan (from 1.9 Dec 1886).

1891-1892 _ 0.5 _ 18 Dec to 17 Jan (from 2.3 Jan 1892).

1954-1955 _ 0.2 _ 11 Feb to 13 Mar (from 1.2 Feb 1955).

The coldest months without subzero outcomes for any 31-d interval ...

0.3 Jan 1815 (0.3), 

0.4 Dec 1844 (0.2), 0.4 Jan 1945 (0.3)

0.5 Dec 1846 (0.5), 0.5 Jan 1941 (0.5)

0.6 Jan 1774 (0.5). 0.6 Jan 1842 (0.5).

===============================================================

Some historical trends involved in this coldest 31-d statistic, including from the pre-daily era of 1659 to 1771.

__ (the Dec means shown are for the years previous to the Jans and Febs, so for example 1772-1801 shows Dec 1771 to 1800.

Interval _____ Mean coldest 31-d _____ Mean coldest calendar month ____ Mean coldest months D-F

1659-1771 ___ n/a est 1.4 ___________ 2.1 _________________________ (3.8) 2.9 (3.5)

1772-1801 ___ 1.1 _________________ 1.7 _________________________ (3.5) 2.5 (3.9)

1802-1831 ___ 1.1 _________________ 1.9 _________________________ (3.9) 2.3 (4.0)

1832-1861 ___ 1.4 _________________ 2.1 _________________________ (4.3) 3.2 (3.7)

1862-1891 ___ 1.6 _________________ 2.4 _________________________ (3.7) 3.5 (4.4)

1892-1921 ___ 2.1 _________________ 2.9 _________________________ (4.5) 3.9 (4.1)

1922-1951 ___ 2.1 _________________ 2.7 _________________________ (4.5) 3.8 (4.1)

1952-1981 ___ 2.0 _________________ 2.7 _________________________ (4.7) 3.6 (3.7)

1982-2011 ___ 2.5 _________________ 3.2 _________________________ (4.6) 4.4 (4.5)

1990-2019 ___ 2.9 _________________ 3.7 _________________________ (4.9) 4.7 (4.9)

 

 

 

Edited September 13, 2019 by Roger J Smith

[Roger J Smith]

Data for the winters 1940 to present

Winter _ coldest 31d __ duration ___ coldest cal month involved ____ (cases with colder cal month, and 31-d assoc)

1939-40 _ --1.4 ______ 1-31 Jan ____ Jan --1.4 _________________

1940-41 _ +0.5 ______ 1-31 Jan ____ Jan +0.5 _________________

1941-42 __ 0.0 ______ 10 J - 9 F ____Jan +0.1 _________________

1942-43 __ 4.2 ______ 25 D - 24 J ___Jan +4.9 _________________

1943-44 __ 2.7 ______ 9 F - 10 M ___ Feb +3.6 _________________ +3.5 Dec 43 __ 3.4 16 N - 16 D

1944-45 __ 0.3 ______ 30 D - 29 J ___ Jan +0.4 _________________

1945-46 __ 2.3 ______ 28 D - 27 J ___ Jan +2.7 _________________

1946-47 _ --2.5 ______ 26 J - 25 F ___ Feb --1.9 _________________

1947-48 __ 4.3 ______ 5 F - 6 M _____ Feb +4.7 _________________ (4.4 from 24 N to 24 D, Dec +5.1)

1948-49 __ 4.0 ______ 16 D - 15 J ____Jan +5.5 _________________ +5.1 Mar __ 4.9 19 F - 21 M

1949-50 __ 2.5 ______ 16 J - 15 F ____ Jan +4.2 _________________

1950-51 __ 0.9 ______ 3 D - 2 J ______ Dec +1.2 _________________

1951-52 __ 1.4 ______ 17 J - 16 F ____ Jan +2.7 __________________

1952-53 __ 1.8 ______ 17 N - 17 D ____ Dec +2.8 _________________

1953-54 __ 1.1 ______ 22 J - 21 F _____ Feb +2.6 _________________

1954-55 _ +0.2 ______ 11 F - 13 M _____Feb +1.2 _________________

1955-56 __ 0.0 ______ 29 J - 28 F _____ Feb --0.2 _________________

1956-57 __ 4.0 ______ 18 D - 17 J _____Jan +5.5 _________________ +5.3 Feb __ +5.4 2/6 F - 4/8 M

1957-58 __ 2.7 ______ 22 F - 24 M _____Mar +3.7 _________________+3.4 Jan __ +3.2 10 J - 9 F

1958-59 __ 1.4 ______ 4 J - 3 F _______ Jan +1.6 _________________

1959-60 __ 3.4 ______ 25 J - 24 F _____ Jan +3.8 _________________

1960-61 __ 3.2 ______ 6 D - 5 J _______ Dec, Jan +3.9 _____________

1961-62 __ 0.9 ______ 15 D - 14 J _____ Dec +2.2 _________________ (+1.8 22 F - 24 M, Mar +2.8)

1962-63 _ --2.7 ______ 26 D - 25 J _____ Jan --2.1 _________________ (--2.6 for 7 J to 6 F).

1963-64 __ 2.4 ______ 5(18) D - 4(17) J _ Dec +2.6 _________________

1964-65 __ 2.3 ______ 8 F - 10 M ______ Feb +3.1 _________________

1965-66 __ 1.6 ______ 25 D - 24 J _____ Jan +2.9 __________________

1966-67 __ 3.7 ______ 24 D - 23 J _____ Jan +4.5 __________________

1967-68 __ 1.8 ______ 2 F - 3 M _______ Feb +1.9 __________________ 

1968-69 __ 1.0 ______ 2 F - 4 M _______ Feb +1.0 __________________

1969-70 __ 1.9 ______ 11 F - 13 M _____ Feb +2.9 __________________ (+2.0 from 11 Dec to 10 Jan)

1970-71 __ 2.5 ______ 7 D - 6 J _______ Dec +4.3 __________________

1971-72 __ 3.4 ______ 25 J - 24 F ______ Jan +3.9 __________________

1972-73 __ 3.8 ______ 22 D - 21 J ______ Jan +4.5 __________________ +4.3 Feb 73 __ (+4.2 13 F - 15 M)

1973-74 __ 3.9 ______ 17 (25) N - 17 (25) D_Dec +4.9 _________________

1974-75 __ 4.0 ______ 10 M - 9 A _______ Mar +4.8 _________________ +4.4 Feb 75 __ (+4.6 1 F - 3 M)

1975-76 __ 2.6 ______ 23 J - 22 F _______ Feb +4.5 _________________

1976-77 __ 2.0 ______ 29 N - 29 D ______ Dec +2.0 __________________ (+2.0 sev'l other int, as late as 18 Dec - 17 Jan)

1977-78 __ 1.9 ______ 22 J - 21 F _______ Feb +2.8 __________________

1978-79 _ --0.5 ______ 30 D - 29 J _______ Jan --0.4 __________________

1979-80 __ 1.8 ______ 20 D - 19 J _______ Jan +2.3 ___________________

(to be completed in next post)

 

 

 

 

 

[Roger J Smith]

Winter _ coldest 31d __ duration ___ coldest cal month involved ____ (cases with colder cal month, and 31-d assoc)

1980-81 __ 3.1 ______ 29 J - 28 F ____ Feb +3.0 _________________

1981-82 _ --0.3 ______ 16 D - 15 J ____ Dec +0.3 _________________

1982-83 __ 1.9 ______ 30 J - 1 M _____ Feb +1.7 _________________

1983-84 __ 3.1 ______ 19 J - 18 F ____ Feb +3.3 __________________

1984-85 _ +0.5 ______ 27 D - 26 J ____ Jan +0.8 __________________

1985-86 _ --1.0 ______ 1 F - 3 M ______ Feb --1.1 _________________

1986-87 _ +0.4 ______ 3 J - 2 F _______ Jan +0.8 _________________

1987-88 __ 4.2 ______ 16 N - 16 D _____Dec +5.6 _________________ +4.9 Feb 88 __ (4.4 14 J - 13 F and 4 F - 5 M)

1988-89 __ 4.9 ______ 29 Oct - 28 N ___ Nov +5.2 _________________

1989-90 __ 4.1 ______ 19 N - 19 D _____Dec +4.9 _________________ (also 14 N - 14 D, 22 N - 22 D)

1990-91 _ +0.3 ______ 22 J - 21 F _____ Feb +1.5 __________________

1991-92 __ 2.8 _______ 9 J - 8 F ______ Jan +3.7 __________________

1992-93 __ 2.7 _______ 5 D - 4 J ______ Dec +3.6 __________________

1993-94 __ 3.4 ______ 27 J - 26 F _____ Feb +3.2 ___________________

1994-95 __ 4.3 ______ 14 D - 13 J _____ Jan +4.8 ___________________

1995-96 __ 1.4 ______ 22 J - 21 F _____ Feb +2.5 __________________ +2.3 Dec 95 __ +1.7 from 5 D to 4 J

1996-97 __ 1.4 ______ 22 D - 21 J _____ Jan +2.5 __________________

1997-98 __ 4.6 ______ 11 J - 10 F _____ Jan +5.2 __________________

1998-99 __ 4.8 ______ 11 N - 11 D _____ Dec +5.5 _________________ +5.3 Feb 99 __ 5.0 from 16 J to 15 F

1999-2000_ 4.3 ______27 D - 26 J _____ Jan +4.9 __________________

2000-01 __ 2.3 ______ 23 D - 22 J _____ Jan +3.2 __________________

2001-02 __ 2.3 ______ 9 D - 8 J _______ Dec +3.6 __________________

2002-03 __ 3.7 ______ 27 J - 28 M _____ Feb +3.9 __________________

2003-04 __ 3.9 ______ 12 F - 13 M _____ Feb +5.4 __________________ +4.8 Dec 2003 _ +4.2 5 Dec to 4 Jan

2004-05 __ 3.2 ______12 F - 14 M _____ Feb +4.3 __________________

2005-06 __ 3.1 ______ 20 F - 22 M _____ Feb +3.7 __________________

2006-07 __ 4.7 ______ 20 J - 19 F ______Feb +5.8 __________________ highest value of coldest calendar month

2007-08 __ 4.1 ______ 9 D - 8 J _______ Dec +4.9 __________________

2008-09 __ 2.4 ______ 26 D - 25 J _____ Jan +3.0 __________________

2009-10 __ 0.0 ______ 14 D - 13 J _____ Jan +1.4 __________________

2010-11 _ --1.5 ______ 26 N - 26 D _____ Dec --0.7 __________________

2011-12 __ 2.1 ______ 13 J - 12 F ______ Feb +3.8 __________________

2012-13 __ 2.3 ______ 10 M - 9 A ______ Mar +2.7 __________________ also +2.3 from 12 J to 11 F

2013-14 __ 5.3 ______ 14 J - 13 F _____ Jan +5.7 __________________highest value of coldest 31-d interval

2014-15 __ 2.8 ______ 14 J - 13 F _____ Jan +4.0 __________________

2015-16 __ 4.0 ______ 10 F - 11 M _____ Feb +4.9 __________________

2016-17 __ 3.6 ______ 28 D - 27 J _____ Jan +4.0 __________________

2017-18 __ 2.4 ______ 2 F - 4 M _______ Feb +2.9 __________________

2018-19 __ 3.6 ______ 3 J - 4 F _______ Jan +4.0 __________________