"There is always so much concentration on snow...but obviously temps are just as if not more important to discern any trends.
Here is Detroit's temperature data for all El Ninos since the 1870s. Warmer than normal is in red, colder in blue, and temps that were +/- 0.5F of normal are in black.
AVERAGE TEMPS
SEP: 64.4...OCT: 52.4...NOV: 41.5...DEC: 30.1...JAN: 25.6...FEB: 28.1...MAR: 37.2...APR: 49.2
Ironically...the most discernable trend of ANY month in ANY strength Nino is a cooler than normal September during strong Ninos. Yet our dominant cool pattern this year has let up for a September thats on track to be warmer than normal

STRONG EL NINOS
Season -- SEP -- OCT -- NOV -- DEC -- JAN -- FEB -- MAR -- APR
1877-78 -- 64.3 -- 53.8 -- 39.2 -- 38.1 -- 27.3 -- 29.2 -- 41.3 -- 53.4
1888-89 -- 60.0 -- 46.9 -- 41.4 -- 31.4 -- 29.8 -- 19.4 -- 37.4 -- 46.3
1896-97 -- 59.6 -- 47.6 -- 40.5 -- 30.3 -- 23.0 -- 27.4 -- 34.6 -- 45.2
1899-00 -- 59.7 -- 56.0 -- 42.8 -- 28.7 -- 28.3 -- 21.3 -- 26.3 -- 48.3
1902-03 -- 62.2 -- 52.4 -- 46.9 -- 26.9 -- 24.1 -- 25.6 -- 41.5 -- 46.9
1940-41 -- 62.8 -- 51.1 -- 38.0 -- 32.0 -- 26.3 -- 25.3 -- 30.5 -- 52.6
1957-58 -- 62.9 -- 50.8 -- 41.0 -- 34.1 -- 26.6 -- 22.8 -- 36.3 -- 49.6
1972-73 -- 63.0 -- 47.3 -- 37.4 -- 29.3 -- 28.8 -- 25.3 -- 43.3 -- 48.8
1982-83 -- 61.8 -- 52.5 -- 41.6 -- 37.3 -- 28.7 -- 31.6 -- 38.3 -- 44.2
1991-92 -- 63.1 -- 54.8 -- 38.5 -- 32.1 -- 28.3 -- 30.8 -- 35.5 -- 46.3
1997-98 -- 62.7 -- 51.7 -- 37.1 -- 32.2 -- 32.8 -- 36.7 -- 39.5 -- 50.4
MODERATE EL NINOS
Season -- SEP -- OCT -- NOV -- DEC -- JAN -- FEB -- MAR -- APR
1911-12 -- 64.2 -- 50.9 -- 35.9 -- 33.9 -- 13.1 -- 18.3 -- 26.4 -- 46.2
1914-15 -- 62.8 -- 56.6 -- 39.7 -- 23.8 -- 23.4 -- 29.9 -- 31.9 -- 52.2
1918-19 -- 57.4 -- 55.5 -- 42.3 -- 36.3 -- 31.0 -- 29.4 -- 36.3 -- 45.9
1925-26 -- 66.1 -- 44.5 -- 38.1 -- 26.9 -- 25.4 -- 25.8 -- 29.0 -- 40.9
1930-31 -- 66.3 -- 51.6 -- 42.0 -- 29.6 -- 28.4 -- 32.8 -- 34.1 -- 48.6
1941-42 -- 67.5 -- 55.2 -- 43.0 -- 35.5 -- 25.8 -- 22.7 -- 38.5 -- 52.9
1965-66 -- 66.2 -- 51.2 -- 42.6 -- 35.9 -- 21.4 -- 28.3 -- 38.3 -- 44.4
1968-69 -- 65.5 -- 53.4 -- 41.0 -- 28.1 -- 23.1 -- 28.3 -- 33.4 -- 49.4
1986-87 -- 65.9 -- 52.6 -- 37.3 -- 31.3 -- 26.1 -- 29.6 -- 39.7 -- 50.8
1994-95 -- 66.2 -- 53.7 -- 45.5 -- 35.4 -- 28.3 -- 24.9 -- 39.1 -- 45.6
2002-03 -- 68.9 -- 50.0 -- 39.2 -- 28.7 -- 20.5 -- 23.1 -- 35.6 -- 48.4
2006-07 -- 62.0 -- 49.7 -- 42.6 -- 37.4 -- 29.6 -- 19.3 -- 40.1 -- 47.7
2009-10 -- 66.0 -- 50.0 -- 45.3 -- 29.3 -- 25.1 -- 27.8 -- 42.4 -- 52.4
WEAK EL NINOS
Season -- SEP -- OCT -- NOV -- DEC -- JAN -- FEB -- MAR -- APR
1904-05 -- 63.7 -- 50.5 -- 40.1 -- 25.8 -- 20.3 -- 17.9 -- 37.5 -- 44.4
1905-06 -- 65.3 -- 52.1 -- 37.5 -- 31.9 -- 33.6 -- 25.6 -- 28.2 -- 49.2
1923-24 -- 64.0 -- 51.8 -- 40.4 -- 37.7 -- 21.8 -- 25.5 -- 33.7 -- 46.0
1939-40 -- 65.9 -- 52.9 -- 38.9 -- 33.5 -- 19.0 -- 26.7 -- 28.6 -- 42.8
1951-52 -- 62.5 -- 55.4 -- 34.6 -- 28.4 -- 29.3 -- 29.3 -- 34.3 -- 49.5
1953-54 -- 64.7 -- 56.8 -- 44.5 -- 33.6 -- 26.0 -- 33.5 -- 33.5 -- 50.1
1963-64 -- 63.1 -- 62.7 -- 46.0 -- 23.8 -- 30.4 -- 28.9 -- 36.1 -- 49.3
1969-70 -- 64.8 -- 51.4 -- 37.9 -- 26.4 -- 16.6 -- 24.4 -- 32.8 -- 49.3
1976-77 -- 62.1 -- 47.3 -- 33.5 -- 21.5 -- 12.8 -- 25.2 -- 41.4 -- 52.5
1977-78 -- 65.0 -- 47.9 -- 40.5 -- 25.5 -- 19.5 -- 16.3 -- 30.0 -- 45.5
2004-05 -- 67.4 -- 53.3 -- 43.0 -- 29.7 -- 24.1 -- 28.4 -- 33.2 -- 50.7
Some Detroit temp data for Ninos.
This September is clearly going to be a warm September. Not only a surprise in a cool year, but it has literally never before happened in the small sample size that we have that is the strong Nino. The only warm Sept in a borderline strong Nino was 2009, however I was informed that has been officially classified as mod. In that case, there has NOT been a warmer than normal September in the 10 strong Nino events on record since 1877.
Warm Septembers are more common in moderate Ninos however.
Even though there have been 0 warm Septembers in the 10 strong Ninos on record, in the 34 El Nino years of any strength (since 1877), there HAVE been 13 warm Septembers. Those 13 warm Septembers paved the way for a very even split of winters. 5 winters were cold, 5 winters were mild, and 3 were near normal.
If we are just talking a very warm September (nino or not), of the top 20 warmest Septembers on record, 10 of the following winters were colder than normal, 4 were near normal, and 6 were warmer than normal.
In all the years I concentrated on snow data/patterns during Ninos, this is the first year I concentrated on temps. I was shocked to find some of the results, especially how once you take out the infamous winters of 1982-83 & 1997-98, strong Nino does not scream warm winter at all.
Also of interest is how frequently in an El Nino (of any strength) we would see one unusually warm month and one unusually cold month in met winter. In several of the warm winters there was still a very cold month, and in several of the cold winters that was a very mild month. Often times it was Dec that was warm & Feb that was cold, but by no means is that a sure thing.
STRONG EL NINOS
1 warmer than normal Fall
2 near normal Falls
8 colder than normal Falls
4 warmer than normal Winters
3 near normal Winters
4 colder than normal Winters
MODERATE EL NINOS
3 warmer than normal Fall
5 near normal Falls
5 colder than normal Falls
6 warmer than normal Winters
2 near normal Winters
5 colder than normal Winters
WEAK EL NINOS
1 warmer than normal Fall
3 near normal Falls
7 colder than normal Falls
3 warmer than normal Winters
3 near normal Winters
5 colder than normal Winters
ALL EL NINOS SINCE 1877
7 warmer than normal Falls
8 near normal Falls
20 colder than normal Falls
13 warmer than normal Winters
8 near normal Winters
14 colder than normal Winters