Addendum to ‘How unusual were US winters in the Carter and early Reagan eras? An analysis using extended winter temperatures’

In ‘How unusual were US winters in the Carter and early Reagan eras? An analysis using extended winter temperatures’ I attempted to see if the period was as unusual as thought by authors Karl, Livezey and Epstein in their ‘Recent Unusual Mean Winter Temperatures Across the Contiguous United States’. As I suspected, when we either:

1. extend the winter to a November to March or October to March period, or
2. in the Midwest at least, extend the series back to the 1870s

we find that the period form 1975/1976 to 1983/1984 is less abnormal than made out by the article. Point 2) may not apply to the South or the West: data for both regions in the middle 1870s are very sparse. What data exists, illustrated by the table below for Galveston in Texas and Wilmington in North Carolina, suggest that the run of extreme winters over the Midwest in the late 1870s and 1880s extended to the West South Central states [Texas, Oklahoma, Arkansas, Louisiana] but not to the East South Central or South Atlantic states, nor to west of the Continental Divide.

	Galveston, Texas				Wilmington, North Carolina
	Winter (˚C)	σ	October to March (˚C)	σ	Winter (˚C)	σ	October to March (˚C)	σ
1871/1872					6.867	-1.152	10.083	-1.418
1872/1873					7.833	-0.586	10.400	-1.139
1873/1874	13.23	+0.14	15.97	+0.03	9.333	+0.293	11.567	-0.111
1874/1875	12.00	-0.65	15.37	-0.55	7.600	-0.722	11.017	-0.596
1875/1876	15.53	+1.61	16.98	+1.01	11.233	+1.406	12.300	+0.535
1876/1877	10.60	-1.55	14.17	-1.70	7.200	-0.956	10.133	-1.374
1877/1878	12.17	-0.55	15.22	-0.69	9.167	+0.195	12.600	+0.799
1878/1879	11.20	-1.17	15.38	-0.53	7.267	-0.917	11.067	-0.552
1879/1880	15.60	+1.66	17.57	+1.57	12.733	+2.284	14.167	+2.179
1880/1881	10.53	-1.60	13.32	-2.52	7.400	-0.839	10.350	-1.183
1881/1882	15.23	+1.42	17.67	+1.67	11.533	+1.582	14.117	+2.135
1882/1883	12.13	-0.57	15.67	-0.26	9.833	+0.586	12.267	+0.505
1883/1884	12.80	-0.14	16.45	+0.50	10.933	+1.230	13.517	1.607
1884/1885	11.60	-0.91	15.00	-0.90	9.300	+0.274	12.033	+0.300
1885/1886	11.17	-1.19	14.43	-1.44	7.367	-0.859	10.533	-1.022
1886/1887	13.63	+0.39	16.22	+0.27	9.000	+0.098	11.583	-0.097
1887/1888	12.20	-0.53	15.13	-0.77	9.067	+0.137	10.950	-0.655
1888/1889	13.07	+0.03	15.65	-0.27	8.367	-0.273	11.183	-0.449
1889/1890	18.17	+3.31	18.12	+2.10	14.000	+3.026	13.950	+1.988
1890/1891	13.67	+0.42	16.10	+0.16	10.167	+0.781	12.250	+0.491
1891/1892	12.93	-0.05	15.35	-0.56	9.267	+0.254	10.900	-0.699
1892/1893	13.17	+0.10	16.32	+0.37	7.933	-0.527	10.733	-0.846
1893/1894	14.03	+0.65	16.53	+0.58	10.233	+0.820	12.817	+0.990
1894/1895	10.87	-1.38	14.87	-1.03	6.733	-1.230	10.467	-1.080
1895/1896	12.87	-0.10	15.27	-0.64	8.433	-0.234	11.083	-0.537
1896/1897	12.63	-0.25	16.22	+0.27	8.400	-0.254	11.867	+0.153
1897/1898	13.97	+0.61	16.93	+0.96	9.167	+0.195	12.567	+0.770
1898/1899	10.37	-1.70	14.07	-1.80	7.933	-0.527	11.217	-0.420
1899/1900	11.70	-0.85	15.37	-0.55	7.967	-0.507	11.133	-0.493
1900/1901	13.33	+0.20	16.57	+0.61	7.300	-0.898	11.483	-0.185
1901/1902	11.20	-1.17	15.10	-0.80	6.567	-1.327	9.883	-1.594
1902/1903	12.27	-0.48	15.98	+0.05	9.400	+0.332	13.067	+1.210
1903/1904	12.67	-0.23	15.67	-0.26	5.900	-1.718	9.633	-1.815
1904/1905	10.30	-1.75	14.80	-1.09	6.000	-1.659	10.000	-1.492
1905/1906	11.43	-1.02	14.97	-0.93	8.767	-0.039	11.317	-0.332
1906/1907	16.23	+2.06	18.03	+2.02	9.033	+0.117	12.217	+0.461
1907/1908	13.07	+0.03	16.13	+0.19	8.233	-0.351	11.317	-0.332
1908/1909	14.43	+0.91	16.55	+0.59	10.967	+1.250	12.817	+0.990
1909/1910	11.57	-0.93	16.32	+0.37	7.800	-0.605	11.500	-0.170
1910/1911	15.33	+1.49	17.62	+1.62	9.033	+0.117	11.350	-0.302
1911/1912	11.00	-1.30	14.07	-1.80	7.467	-0.800	10.967	-0.640
1912/1913	12.77	-0.16	15.53	-0.39	11.167	+1.367	13.050	+1.196
1913/1914	12.83	-0.12	15.40	-0.51	8.700	-0.078	10.867	-0.728
1914/1915	11.53	-0.95	14.32	-1.56	8.700	-0.078	10.883	-0.713
1915/1916	14.57	+0.99	17.55	+1.55	9.133	+0.176	12.000	+0.270
1916/1917	13.97	+0.61	16.47	+0.51	9.700	+0.508	12.350	+0.579
1917/1918	11.40	-1.04	15.12	-0.79	6.100	-1.601	9.867	-1.609
1918/1919	12.33	-0.44	15.25	-0.66	9.733	+0.527	12.383	+0.608
1919/1920	13.67	+0.42	16.72	+0.75	7.933	-0.527	12.100	+0.359
1920/1921	14.10	+0.69	16.62	+0.66	9.567	+0.430	12.850	+1.019
1921/1922	14.07	+0.67	16.78	+0.82	9.400	+0.332	12.483	+0.696
1922/1923	15.67	+1.70	17.08	+1.11	9.867	+0.605	12.500	+0.711
1923/1924	12.73	-0.18	15.05	-0.85	9.533	+0.410	11.383	-0.273
1924/1925	13.10	+0.05	16.83	+0.87	10.067	+0.723	12.450	+0.667
1925/1926	11.80	-0.78	14.72	-1.17	8.800	-0.019	11.000	-0.611
1926/1927	15.47	+1.57	17.38	+1.39	10.900	+1.211	12.850	+1.019
1927/1928	12.03	-0.63	16.47	+0.51	9.367	+0.313	12.383	+0.608
1928/1929	12.17	-0.55	15.92	-0.02	9.233	+0.234	12.533	+0.740
1929/1930	12.13	-0.57	14.60	-1.28	10.233	+0.820	12.267	+0.505
1930/1931	12.87	-0.10	14.97	-0.93	8.333	-0.293	10.533	-1.022
1931/1932	15.70	+1.72	17.82	+1.81	13.667	+2.831	14.617	+2.576
1932/1933	13.43	+0.27	15.63	-0.29	11.467	+1.543	13.117	+1.254
1933/1934	15.43	+1.55	17.58	+1.59	9.233	+0.234	11.683	-0.009
1934/1935	14.00	+0.63	17.57	+1.57	8.600	-0.136	12.333	+0.564
1935/1936	11.43	-1.02	15.57	-0.35	6.233	-1.523	10.933	-0.669
1936/1937	13.90	+0.57	15.58	-0.34	11.467	+1.543	13.067	+1.210
1937/1938	13.63	+0.39	16.45	+0.50	9.133	+0.176	11.917	+0.197
1938/1939	14.17	+0.74	16.78	+0.82	10.933	+1.230	13.283	+1.401
1939/1940	11.30	-1.10	14.77	-1.12	6.700	-1.249	10.300	-1.227
1940/1941	13.73	+0.46	15.85	-0.08	8.333	-0.293	10.900	-0.699
1941/1942	12.57	-0.29	15.62	-0.31	8.167	-0.390	12.350	+0.579
1942/1943	13.87	+0.54	16.53	+0.58	9.067	+0.137	12.133	+0.388
1943/1944	13.47	+0.29	15.78	-0.15	9.200	+0.215	11.667	-0.023
1944/1945	13.43	+0.27	16.82	+0.85	8.100	-0.429	11.950	+0.226
1945/1946	12.87	-0.10	16.35	+0.40	8.533	-0.176	12.317	+0.549
1946/1947	12.30	-0.46	15.23	-0.67	9.533	0.410	12.083	+0.344
1947/1948	11.50	-0.98	15.38	-0.53	7.733	-0.644	11.867	+0.153
1948/1949	14.33	+0.84	16.60	+0.64	12.733	2.284	14.050	+2.077
1949/1950	16.70	+2.36	18.00	+1.99	12.467	2.128	13.750	+1.812
1950/1951	13.27	+0.16	16.42	+0.46	8.200	-0.371	11.483	-0.185
1951/1952	15.93	+1.87	17.27	+1.28	10.633	+1.054	12.617	+0.814
1952/1953	13.57	+0.35	16.07	+0.13	9.733	+0.527	11.933	+0.212
1953/1954	14.07	+0.67	16.23	+0.29	10.067	+0.723	12.150	+0.403
1954/1955	13.77	+0.48	16.58	+0.62	7.633	-0.703	11.250	-0.390
1955/1956	14.03	+0.65	16.48	+0.53	7.867	-0.566	10.917	-0.684
1956/1957	16.00	+1.91	17.70	+1.70	11.100	+1.328	12.733	+0.916
1957/1958	12.30	-0.46	14.93	-0.96	6.500	-1.366	9.717	-1.741
1958/1959	11.97	-0.68	15.25	-0.66	7.633	-0.703	10.983	-0.625
1959/1960	11.93	-0.70	14.45	-1.43	8.267	-0.332	10.567	-0.992
1960/1961	11.70	-0.85	15.83	-0.10	7.133	-0.996	11.317	-0.332
1961/1962	13.73	+0.46	15.95	0.02	9.167	+0.195	11.367	-0.288
1962/1963	11.00	-1.30	15.33	-0.58	6.133	-1.581	10.500	-1.051
1963/1964	10.53	-1.60	15.07	-0.84	7.200	-0.956	10.800	-0.787
1964/1965	13.23	+0.14	15.57	-0.35	9.400	+0.332	11.817	+0.109
1965/1966	12.67	-0.23	16.13	+0.19	8.133	-0.410	11.433	-0.229
1966/1967	12.57	-0.29	16.17	+0.22	9.200	+0.215	12.450	+0.667
1967/1968	12.00	-0.65	15.10	-0.80	7.167	-0.976	10.667	-0.904
1968/1969	13.27	+0.16	15.52	-0.40	6.900	-1.132	10.283	-1.242
1969/1970	12.63	-0.25	15.57	-0.35	6.233	-1.523	10.117	-1.389
1970/1971	14.80	+1.14	16.18	+0.24	8.633	-0.117	11.417	-0.243
1971/1972	15.43	+1.55	17.98	+1.97	11.033	+1.289	13.267	+1.386
1972/1973	11.83	-0.76	15.27	-0.64	8.867	+0.020	12.067	+0.329
1973/1974	14.30	+0.82	17.93	+1.92	11.567	+1.601	14.050	+2.077
1974/1975	14.37	+0.87	16.67	+0.70	10.500	+0.976	12.183	+0.432
1975/1976	13.50	+0.31	16.42	+0.46	9.967	+0.664	13.567	+1.651
1976/1977	10.83	-1.40	13.40	-2.44	5.900	-1.718	9.617	-1.829
1977/1978	10.00	-1.94	14.28	-1.59	5.933	-1.698	10.017	-1.477
1978/1979	11.17	-1.19	15.37	-0.55	7.467	-0.800	11.333	-0.317
1979/1980	12.63	-0.25	15.22	-0.69	7.533	-0.761	10.750	-0.831
1980/1981	12.10	-0.59	14.83	-1.06	6.133	-1.581	9.450	-1.976
1981/1982	12.50	-0.33	16.22	+0.27	7.533	-0.761	10.533	-1.022
1982/1983	13.40	+0.24	15.97	+0.03	8.200	-0.371	11.250	-0.390
1983/1984	11.17	-1.19	15.57	-0.35	8.067	-0.449	11.267	-0.376

The table above also suggests that, like in the Midwest, extreme winters in the South may cluster over different periods than for the CONUS as a whole, and that fluctuating extreme winters over the wholse CONUS may in particular regions be only extremes of one type. Note the very warm winters in the South Atlantic, represented by Wilmington, in the early 1880s and the long run of cold winters in the South from 1976/1977 to 1983/1984.

It can also be seen that abnormally cold or warm winters over the entire contiguous US do not necessarily affect the South at all. This occurred in 1916/1917, 1928/1929 and 1978/1979 (cold) and 1952/1953, 1953/1954 and 1975/1976 (warm).

Another point I wished to study in this addendum is the extended winter of 1919/1920. According to the table in my previous blog post the October to March period of 1919/1920 is 1.21 standard deviations colder than the 1896 to 1984 mean, although the actual winter from December to February was only about 0.6 standard deviations colder.

It can also be noted that April 1920 is the coolest over the contiguous US since at least 1895. The map however shows that, unlike 1917/1918 and 1976/1977, the extreme cold was over Canadian border regions, with the result that coal demand was not nearly so great as in 1917/1918. The main reason why this season appears abnormal only in the October to March season is that October 1919 was record cool over large areas of the Northwest, and record heat over the South could not compensate at a national level:

Standardised temperature anomalies for October 1919. Note the massive (over three standard deviations!) opposite-sign anomalies over the South and the Northern Great Plains

Another case omitted from the main section was the winter of 1906/1907. When extended to a November to March period, it is anomalously warm overall in spite of severe cold in the far north and New England, due to an exceptionally warm March. Between 1890 and 2016, the Southern Plains and Gulf Coast never experienced so warm an extended winter.

This winter is better remembered for the extremely persistent and heavy precipitation over most of the West, culminating in major flooding in March 1907 and a record annual flow on the Colorado River. This extremely mild winter outside the northern tier was followed by the “year without a summer” during the ensuing six months. In fact, there were large areas in the Midwest and South where March 1907 was hotter than April 1907. A similar anomaly occurred in the UK where in some places March was the sunniest month of the entire year.

How unusual were US winters in the Carter and early Reagan eras? An analysis using extended winter temperatures

The late 1984 article ‘Recent Unusual Mean Winter Temperatures Across the Contiguous United States’ by Thomas R. Karl, Robert E. Livezey and Edward S. Epstein showed a sequence of extremely unusual winters occurred across the United States beginning with the winter of 1975/1976 and continuing up to the then-current winter of 1983/1984.

Whilst the article is interesting, the knowledge of climate history I have gathered always appears to say that the period of the Great Depression from 1928/1929 to 1936/1937 saw winters as unusual —both in warmth and cold — as the period under review. An earlier analysis I did a year or two ago did not suggest this. This applies even when the two periods are analysed region by region. This last step is very important since I have long noted that many Depression winters saw extreme but opposite sign temperature anomalies in the West and East (and also in Alaska, which under stable global temperatures forms a three-way seesaw with the two contiguous regions). I also noticed studying the article that there was a remarkable absence of extreme winters in the contiguous United States between 1954/1955 and 1974/1975. During these twenty-one years, not one winter was outside 1.179 standard deviations from the mean — an occurrence with probability under 0.2 percent. This is noticed briefly also in ‘Agriculture and the Recent “Benign Climate” in Minnesota’ by Donald G. Baker, David L. Ruschy and Richard H. Skaggs.

As an extension of ‘Recent Unusual Mean Winter Temperatures Across the Contiguous United States’, I have attempted to do an analysis of CONUS temperatures over the extended winter seasons from November to March and from October to March, using the same criteria found in the original study. Karl, Livezey and Epstein showed that a departure of 1.253 standard deviations from the CONUS-averaged mean qualifies a season as “abnormal” in that the proportion of a normal distribution outside such a range is less than one-tenth the complete set of data. However, they also noted a range of 1.179 standard deviations from the mean to give a slightly less rigid definition of an “unusual” season. With this noted, I will analyse the extended winter seasons to see if they produced the same abnormalities Karl, Livezey and Epstein noticed for the December to February season.

November to March:

Mean area-averaged contiguous US temperature from November to March between 1895/1896 and 1983/1984, with mean shown with dashed line and 1.179 standard deviations above and below mean with solid line

Year	Contiguous U.S. Average T, November to March (˚C)	Standardised anomaly
1895/1896	1.71	-0.46
1896/1897	1.58	-0.64
1897/1898	2.08	+0.06
1898/1899	-0.02	-2.84
1899/1900	2.52	+0.66
1900/1901	2.02	-0.03
1901/1902	1.81	-0.33
1902/1903	1.77	-0.37
1903/1904	1.29	-1.03
1904/1905	1.59	-0.63
1905/1906	1.77	-0.38
1906/1907	3.03	+1.36
1907/1908	2.76	+0.99
1908/1909	2.61	+0.78
1909/1910	2.11	+0.09
1910/1911	2.63	+0.81
1911/1912	0.12	-2.66
1912/1913	1.53	-0.70
1913/1914	2.58	+0.74
1914/1915	1.28	-1.05
1915/1916	2.18	+0.19
1916/1917	0.65	-1.92
1917/1918	1.84	-0.27
1918/1919	2.21	+0.23
1919/1920	1.26	-1.09
1920/1921	3.41	+1.89
1921/1922	1.87	-0.24
1922/1923	1.98	-0.08
1923/1924	1.91	-0.18
1924/1925	2.40	+0.49
1925/1926	2.28	+0.33
1926/1927	2.61	+0.78
1927/1928	2.44	+0.55
1928/1929	1.26	-1.09
1929/1930	1.82	-0.30
1930/1931	2.51	+0.65
1931/1932	2.67	+0.87
1932/1933	1.77	-0.38
1933/1934	3.46	+1.95
1934/1935	3.20	+1.60
1935/1936	0.69	-1.86
1936/1937	1.08	-1.33
1937/1938	2.96	+1.27
1938/1939	2.28	+0.33
1939/1940	2.13	+0.13
1940/1941	2.22	+0.24
1941/1942	2.32	+0.39
1942/1943	2.26	+0.29
1943/1944	2.06	+0.02
1944/1945	2.61	+0.78
1945/1946	2.68	+0.88
1946/1947	2.21	+0.23
1947/1948	1.03	-1.40
1948/1949	1.42	-0.86
1949/1950	2.59	+0.76
1950/1951	1.88	-0.23
1951/1952	1.61	-0.60
1952/1953	3.27	+1.69
1953/1954	3.24	+1.65
1954/1955	2.05	+0.01
1955/1956	1.55	-0.68
1956/1957	2.55	+0.70
1957/1958	2.06	+0.02
1958/1959	2.07	+0.04
1959/1960	1.17	-1.21
1960/1961	2.63	+0.82
1961/1962	1.26	-1.08
1962/1963	2.09	+0.07
1963/1964	1.56	-0.66
1964/1965	1.57	-0.65
1965/1966	2.34	+0.42
1966/1967	2.83	+1.09
1967/1968	2.12	+0.10
1968/1969	1.04	-1.38
1969/1970	1.78	-0.36
1970/1971	1.94	-0.14
1971/1972	2.57	+0.72
1972/1973	1.81	-0.33
1973/1974	2.97	+1.28
1974/1975	2.21	+0.23
1975/1976	3.19	+1.58
1976/1977	1.30	-1.02
1977/1978	1.25	-1.09
1978/1979	0.38	-2.30
1979/1980	2.14	+0.14
1980/1981	3.26	+1.68
1981/1982	2.13	+0.13
1982/1983	3.26	+1.67
1983/1984	1.64	-0.55

October to March:

Mean area-averaged contiguous US temperature from October to March between 1895/1896 and 1983/1984, with mean shown with dashed line and 1.179 standard deviations above and below mean with solid line

Year	Contiguous U.S. Average T, October to March (˚C)	Standardised anomaly
1895/1896	3.17	-0.87
1896/1897	3.16	-0.89
1897/1898	3.87	+0.19
1898/1899	1.79	-2.98
1899/1900	4.13	+0.59
1900/1901	3.94	+0.30
1901/1902	3.67	-0.11
1902/1903	3.56	-0.29
1903/1904	3.11	-0.97
1904/1905	3.36	-0.59
1905/1906	3.29	-0.69
1906/1907	4.43	+1.04
1907/1908	4.32	+0.87
1908/1909	4.01	+0.40
1909/1910	3.69	-0.08
1910/1911	4.37	+0.96
1911/1912	2.01	-2.64
1912/1913	3.24	-0.77
1913/1914	3.97	+0.34
1914/1915	3.22	-0.81
1915/1916	3.98	+0.36
1916/1917	2.41	-2.04
1917/1918	3.24	-0.77
1918/1919	4.08	+0.52
1919/1920	2.95	-1.21
1920/1921	4.94	+1.82
1921/1922	3.72	-0.04
1922/1923	3.78	+0.06
1923/1924	3.37	-0.57
1924/1925	4.13	+0.58
1925/1926	3.47	-0.42
1926/1927	4.30	+0.85
1927/1928	4.25	+0.77
1928/1929	3.18	-0.86
1929/1930	3.55	-0.30
1930/1931	3.92	+0.26
1931/1932	4.50	+1.15
1932/1933	3.35	-0.60
1933/1934	5.03	+1.96
1934/1935	4.94	+1.82
1935/1936	2.59	-1.75
1936/1937	2.89	-1.31
1937/1938	4.49	+1.14
1938/1939	4.16	+0.64
1939/1940	3.88	+0.20
1940/1941	4.08	+0.51
1941/1942	4.08	+0.52
1942/1943	3.97	+0.34
1943/1944	3.72	-0.03
1944/1945	4.33	+0.89
1945/1946	4.28	+0.81
1946/1947	3.80	+0.08
1947/1948	3.34	-0.62
1948/1949	3.14	-0.92
1949/1950	4.20	+0.69
1950/1951	3.92	+0.27
1951/1952	3.37	-0.57
1952/1953	4.66	+1.40
1953/1954	4.94	+1.82
1954/1955	3.81	+0.09
1955/1956	3.42	-0.49
1956/1957	4.36	+0.94
1957/1958	3.53	-0.32
1958/1959	3.83	+0.14
1959/1960	2.94	-1.22
1960/1961	4.30	+0.85
1961/1962	3.07	-1.03
1962/1963	3.98	+0.36
1963/1964	3.83	+0.14
1964/1965	3.33	-0.64
1965/1966	4.08	+0.52
1966/1967	4.29	+0.83
1967/1968	3.79	+0.07
1968/1969	2.97	-1.19
1969/1970	3.25	-0.75
1970/1971	3.49	-0.39
1971/1972	4.28	+0.81
1972/1973	3.38	-0.55
1973/1974	4.71	+1.47
1974/1975	3.86	+0.18
1975/1976	4.75	+1.53
1976/1977	2.74	-1.53
1977/1978	3.08	-1.02
1978/1979	2.39	-2.07
1979/1980	3.94	+0.30
1980/1981	4.62	+1.34
1981/1982	3.66	-0.13
1982/1983	4.68	+1.43
1983/1984	3.50	-0.37

Analysis and Conclusions:

The tables above suggest that, when we extend the winter season to November to March, and to October to March, we find that the period from 1975/1976 to 1983/1984 was not so unusual as Karl, Livezey and Epstein suggested. Only four of the nine November to March periods were outside the range described in their article, and only five of the nine October to March periods.

We also find that the period from 1954/1955 to 1974/1975 was not so exceptional for lacking extremes when we extend the winter season. Based on a November to March or an October to March period, 1959/1960 and 1968/1969 were “unusually” cold, and 1973/1974 unusually warm, though 1959/1960 is a marginal case on both periods, and October 1968 to March 1969 is likewise. 1973/1974, though, is especially warm in the Deep South, where January 1974 remains the warmest on record in South Carolina, Georgia and Florida.

Standardized contiguous US temperature anomalies relative to 1895 to 2000 mean for October 1959 to March 1960. Note area in southeastern Nebraska and northern Kansas over two standard deviations below the mean, and extensive area in West South Central and Plains colder than 1.5 standard deviations below the mean

Standardized contiguous US temperature anomalies relative to 1895 to 2000 mean for October 1973 to March 1974. Note wide area of the South hotter than 1.5 standard deviations above average.

Standardized contiguous US temperature anomalies relative to 1895 to 2000 mean for November 1968 to March 1969. Note widespread area colder than 1.5 standard deviations below mean from Florida to Montana

We can also note that the winter of 1981/1982 is slightly above normal when measured on the basis of November to March, and only slightly below on an October to March basis. This is because November 1981 was from coast to coast the hottest since 1949 and at the time the sixth-hottest since 1895. Over Minnesota it was the warmest since 1899, over North Dakota the warmest since 1949, and over South Dakota and Nebraska the warmest since 1954, although Monthly Weather Review failed to hint at this via reference to long-term stations there.

November CONUS temperature from 1895 to 1997, with 1895 to 1974 mean of 41.54˚F or 5.3˚C. Note November 1981’s warmth, previously exceeded only by Novembers 1949, 1934, 1913, 1909 and 1899

The very long Fort Snelling, Minnesota record — the oldest temperature station west of the Appalachian Mountains — shows November 1830 and November 1849 as over 1˚C warmer than any November during the twentieth century, not being exceeded until November 2001 when Australian coal barons and Gulf oil sheikhs had taken firm control of the climate. Nonetheless, November 1981 was relative to the preindustrial mean more abnormally warm over the contiguous US overall than January 1982 was cold, so it makes sense that the extended 1981/1982 winter was not cold.

Standardised mean temperature anomalies by climate division over the contiguous US for November 1981. Note the anomalous warmth in the Great Plains and Minnesota (where it was the warmest for 82 years)

The very cold winter of 1977/1978 also appears less abnormal when measured over the extended winter, again largely due to a relatively warm November (though not nearly so warm as November 1981). 1976/1977 is affected by a very warm March, which would lead into the hottest spring/summer season from coast to coast since 1936 (ironically, also the last colder winter!). The winter of 1947/1948, on a November to March basis, also stands out as abnormally cold. [1947/1948 is not exceptional on an October to March basis since October 1947 was exceptionally hot — the hottest by mean minimum temperature of the century, and the second-hottest by mean temperature.]

Standardised divisional temperature anomalies for the period from November 1947 to March 1948. Note the general cold outside of Florida, and the area in the Southwest colder than two standard deviations below the mean

The Depression Era:

An earlier cursory examination, and basic knowledge of contiguous US temperature maps, has made me suggest that the winters discussed by Karl, Livezey and Epstein for the Carter and early Reagan eras were replicated during the Great Depression. The table on page 1304 notes several abnormal winters in the Depression era in 1930/1931 (marginal), 1931/1932, 1933/1934 and 1935/1936. However, at a local divisional level, it is clear that almost all the winters from 1928/1929 to 1936/1937 were highly abnormal. The exceptions I noted were 1929/1930 and 1934/1935, but the former is practically disqualified, for it saw a record cold January followed by a record warm February.

The tables above, however, do show that the extended winters during the 1930s were in fact more abnormal than those of the late 1970s and early 1980s. Five consecutive years from 1933/1934 to 1937/1938 qualify as abnormal based on November to March temperature, and the first four are also abnormal based upon October to March temperature. 1934/1935 is particularly striking despite the winter’s apparent absence of large regional anomalies: in fact it is the equal second-warmest October to March between at least 1883 and 1991:

Standardised divisional anomalies for October 1934 to March 1935. Note departures exceeding plus two standard deviations in Southern Plains, and 2.5 standard deviations in division OK 1

In fact, in climate divisions OK 1 [Cimarron, Texas, Beaver, Harper and Ellis Counties], and KS 7 [Southwest], this was the warmest October to March period until 2016:

For Oklahoma as a whole, 1934/1935 was the warmest October to March until 2000. The extended winter of 1936/1937 featured not merely a record cold January west of the Mississippi, but also general cold in October, November and March. 1937/1938, although only marginal for the list above, and not qualifying by an October to March period at all, was warmer than normal virtually everywhere and substantially so in the South and the Intermountain West:

Divisional monthly mean temperature standardised anomalies relative to 1895 to 2000 mean for November 1937 to March 1938. Note striking absence of cooler than average areas

Thus, this study shows my suspicion that Great Depression-era winters were just as abnormal as those of the late 1970s and early 1980s to be correct. This becomes emphatically true when one observes the extreme regional divides found in several of the early 1930s, and the extreme contrast between then-record cold January 1930 and then-record warm February 1930. All these contrasts were noted eleven years ago here.

Beyond Climate Division Era — A Possible Analogue in the Post-Reconstruction Years:

Some time ago, looking to expand knowledge of US climate history beyond the GISS temperature maps (which go back to 1880), I noticed a possible parallel — at least over the Midwest — between approximately 1875 and 1890. Studying the data for Dubuque, Iowa — where temperature data go back to 1851, or twenty years further than most of the US outside the Northeast — I noticed a large number of abnormal winters during those post-Reconstruction years. I observed especially how six of the twelve warmest winters in Dubuque between 1851 and 1975 occurred in this era:

Mean winter temperature in Dubuque, Iowa from 1851/1852 to 1983/1984 [later year labelled on x-axis], with -1.179σ and +1.179σ marked by solid lines, and all-series mean to 1984 by dashed line.

The graph does show a very clear concentration of abnormal winters between 1875 and 1890. Although a comparison with Fort Snelling, Minnesota suggests the Dubuque shelters in use at this time may have given hotter temperatures than a standard modern shelter, this does not refute the argument for an unusual concentration of abnormal Midwestern winters in the late 1870s and 1880s, and the stark contrast with the 1860s. If we extend the winter seasons for Dubuque as we did in the first experiment in this post, we find that the abnormality of post-Reconstruction winters largely remains, although the warm seasons from 1888/1889 to 1891/1892 become fairly unexceptional:

Mean November to March temperature in Dubuque, Iowa from 1851/1852 to 1983/1984 [later year labelled on x-axis], with -1.179σ and +1.179σ marked by solid lines, and all-series mean to 1984 by dashed line.

Mean November to March temperature in Dubuque, Iowa from 1851/1852 to 1983/1984 [later year labelled on x-axis], with -1.179σ and +1.179σ marked by solid lines, and all-series mean to 1984 by dashed line.

Despite the unexceptional nature of the seasons from 1888/1889 to 1891/1892, there remains a sufficient number of abnormal winters in the 1870s and 1880s to make the “exceptional” period a century later seem much less so. It is unfortunate that for the western half of the United States too few temperature data exist to discover whether the contrast between an absence of extreme winters in the 1860s and an abundance thereof in the 1870s and 1880s was replicated there. Data from Boise, Idaho — the oldest station in the Northwest — suggest that:

1. the winters of the late 1870s and 1880s were less abnormal than in the Midwest, and most are unlikely to be abnormal except when the extended season is used
2. the winters of the 1930s and from the middle 1970s to the middle 1980s were exceptionally abnormal in this region of the United States