La Niña Autumns
in the Upper Mississippi River Valley

Jeff Boyne, NWS La Crosse, WI

What Is La Niña? Temperature
Precipitation
Snowfall

Since 1950, La Niñas have been ongoing during nineteen meteorological autumns (September 1 through November 30).  During these autumns, temperatures have averaged above normal across much of the United States.  The greatest anomalies for above normal temperatures are found from the southern Plains and southwest United States northeast into the Dakotas, Upper Mississippi River Valley, Great Lakes, and New England.  Below-normal temperatures are typically found along the West Coast, and near-normal temperatures in Florida.
Composite Standardized Temperature Anomalies
La Niña Autumn Composite Standardized Temperature Anomalies

During these same autumns, precipitation averages below normal across much of the United States.  The exceptions to this include: the Pacific Northwest, along the East Coast and central Gulf Coast (due to tropical systems), and from the northern Rockies east into Minnesota.
 Composite Standardized Precipitation Anomalies
La Niña Autumn Composite Standardized Precipitation Anomalies

Autumn Temperatures in the Upper Mississippi River Valley

During La Niña autumns, temperatures typically average above normal across the Upper Mississippi River Valley.  This is most pronounced during October and November.  More details on the temperatures, specifically at La Crosse, WI and Rochester, MN, can be found below.

La Crosse, WI

In La Crosse, WI, La Niña autumns are usually warmer than normal.  During the nineteen La Niñas since 1950, the average autumn temperature was 50.3°F.  This was 0.7°F warmer than the 1950-2010 average of 49.6°F.  Comparing these autumns to normal, eleven (57.8%) were above normal, six (31.6%) were below normal, and two (10.5%) were normal.  Seasonal average temperatures have ranged from 47.1°F (1995) to 54.4°F (1998).

In a majority of the cases where the autumn temperatures average near or below, it was due to a colder-than-normal September.  During eleven out of nineteen (57.8%) Septembers, temperatures have averaged below normal.  In every one of these colder-than-normal Septembers, there has been a persistent trough of low pressure located across eastern portions of Canada and the United States, and a ridge of high pressure across the central United States.  This upper air pattern usually brings a continuous supply of cool Canadian air into Wisconsin and the Great Lakes.

La Crosse, WI Average Temperatures during La Nina Autumns
La Niña Autumn
Average Temperatures
in La Crosse, WI
While the La Niña September temperatures have tended to be colder than normal, the opposite occurs during October and November.  La Crosse has seen above normal temperatures during fourteen (73.7%) Octobers and twelve (63.2%) Novembers.   During these two months, the average temperature was warmer than normal during sixteen out nineteen (84.2%) La Niñas.  The average temperature was just over a degree (1.2°F) warmer than the 1950-2010 normal of 43.3°F.  The main reason these months are usually warmer than normal is that an upper level ridge usually establishes itself across the eastern half of United States during October and then remains in place through much of November.  This keeps the winds predominantly southerly across the Upper Mississippi River Valley, which ultimately results in above-normal temperatures. 

The table below provides a monthly break down of autumn temperatures in La Crosse, WI during La Niña.

Breakdown of Monthly Temperatures in La Crosse, WI during La Niña Autumns
Year
Autumn
(SON)
ONI
Average Temperature
Autumn
(SON)
Sep.
Oct.
Nov.
1950
-0.9
50.6
62.5
57.0
32.1
1954
-1.1
49.6
62.1
48.9
37.9
1955
-1.8
48.5
64.1
51.8
29.5
1956
-0.9
50.5
59.5
57.5
34.3
1962
-0.6
49.8
58.8
53.1
37.3
1964
-1.2
49.5
61.0
49.6
37.9
1970
-0.8
49.6
61.4
51.8
35.4
1971
-0.9
52.2
64.3
55.7
36.4
1973
-1.7
52.2
62.6
57.1
36.7
1974
-0.7
48.3
56.9
50.4
37.4
1975
-1.6
50.2
57.4
53.0
40.0
1984
-0.6
48.8
59.0
52.4
35.0
1988
-1.6
48.6
64.6
44.6
36.6
1995
-0.6
47.1
61.4
51.0
28.9
1998
-1.1
54.4
68.8
53.4
40.9
1999
-1.2
51.5
61.8
49.9
43.0
2000
-0.5
50.1
62.7
53.6
34.0
2007
-1.0
52.7
65.6
56.5
36.0
2010 -1.4 50.7 61.2 53.6 37.2
 

SON
Sep.
Oct.
Nov.
La Niña Average 50.3°F 61.9°F 52.7°F 36.1°F
1950-2010 Longterm Average 49.6°F 62.3°F 50.7°F 35.7°F
Difference from Longterm Average +0.7°F -0.4°F +2.0°F +0.4°F
# Below
6
(31.5%)
11
(57.8%)
5
(26.3%)
7
(36.8%)
# Above
11
(57.8%)
8
(42.1%)
14
(73.7%)
12
(63.2%)
# Same
2
(10.5%)
0
(0%)
0
(0%)
0
(0%)

Rochester, MN

In Rochester, MN, La Niña autumns are predominantly warmer than normal.  During the nineteen La Niñas since 1950, the average autumn temperature was 47.6°F.  This was 0.7 °F warmer than the 1950-2010 average of 46.9°F.  Thirteen (68.4%) were above normal and six (31.6%) were below normal. 

Looking at the autumn months individually, September had a nearly even split between below normal (10 or 52.6%) and above normal (9 or 47.4%).  Meanwhile, around seventy-five percent of the Octobers (73.7%) and Novembers (63.2%) had above average temperatures.  This is normally when the upper level ridge is most dominant across the eastern half of the United States.

Rochester, MN Average Temperatures during La Nina Autumns
La Niña Autumn
Average Temperatures
in Rochester, MN

 

Seasonal average temperatures have ranged from 43.4°F (1995) to 50.7°F (2007).
 
The table below provides a monthly break down of autumn temperatures in Rochester, MN during La Niña.

Breakdown of Monthly Temperatures in Rochester, MN during La Niña Autumns
Year
Autumn
(SON)
ONI
Average Temperature
Autumn
(SON)
Sep.
Oct.
Nov.
1950
-0.9
47.4 60.7 53.9 27.3
1954
-1.1
47.8 59.9 46.7 36.8
1955
-1.8
45.8 61.4 49.5 26.3
1956
-0.9
48.4 57.4 55.5 32.0
1962
-0.6
47.9 56.6 50.9 36.2
1964
-1.2
46.0 57.6 46.5 33.8
1970
-0.8
47.4 59.9 49.6 32.6
1971
-0.9
49.9 62.0 53.5 34.2
1973
-1.7
49.4 59.4 53.9 34.6
1974
-0.7
45.8 54.7 49.3 33.4
1975
-1.6
48.9 56.2 52.9 37.5
1984
-0.6
46.3 56.2 49.6 33.1
1988
-1.6
45.1 61.0 42.0 32.5
1995
-0.6
43.4 57.8 46.7 25.7
1998
-1.1
50.1 64.4 49.6 36.3
1999
-1.2
48.4 58.1 47.0 40.1
2000
-0.5
47.2 59.9 51.7 30.0
2007
-1.0
50.7 63.9 54.4 33.7
2010 -1.4 49.1 59.5  52.6 35.1
 
 
SON
Sep.
Oct.
Nov.
La Niña Average
47.6°F
59.3°F
50.3°F
33.2°F
1950-2010 Longterm Average
46.9°F
59.7°F
48.2°F
32.7°F
Difference from Longterm Average
+0.7°F
-0.4°F
+2.1°F
+0.5°F
# Below  6
(31.6%)
 10
(52.6%)
 5
(26.3%)
 7
(36.8%)
# Above 13
(68.4%)
9
(47.4%)
14
(73.7%)
12
(63.2%)
# Same 0
(0%)
0
(0%)
0
(0%)
0
(0%)

 

Autumn Precipitation in the Upper Mississippi River Valley

La Niña autumns are usually drier-than-normal across the Upper Mississippi River Valley.  More details on the precipitation at La Crosse, WI and Rochester, MN can be found below.

La Crosse, WI

In La Crosse, WI, La Niña autumns are usually drier than normal (13 out of 19, 68.4%).  The average precipitation was 6.69 inches, which was 0.66 inches drier than the 1950-2010 average of 7.35 inches.  This dry tendency shows up in all three of the autumn months.  It was drier than normal during thirteen (68.4%) Septembers, and twelve (63.2%) Octobers and Novembers (63.2%).

While autumn precipitation during La Niñas is usually on the dry side of the ledger, they have varied dramatically from just 3.24 inches up to 11.33 inches.

The table below provides a monthly break down of autumn precipitation in La Crosse, WI during La Niña.

La Crosse, WI Precipitation during La Nina Autumns
La Niña Autumn
Precipitation
in La Crosse, WI
Breakdown of Monthly Precipitation in La Crosse, WI during La Niña Autumns
Year
Autumn
(SON)
ONI
Precipitation
Autumn
(SON)
Sep.
Oct.
Nov.
1950
-0.9
3.25"
1.75"
1.01"
0.49"
1954
-1.1
10.21"
4.85"
4.47"
0.89"
1955
-1.8
3.24"
1.23"
1.39"
0.62"
1956
-0.9
4.74"
1.56"
1.52"
1.66"
1962
-0.6
4.74"
2.41"
2.24"
0.09"
1964
-1.2
6.82"
5.48"
0.25"
1.09"
1970
-0.8
11.33"
5.30"
3.43"
2.60"
1971
-0.9
5.72"
2.43"
1.09"
2.20"
1973
-1.7
7.67"
3.68"
2.06"
1.93"
1974
-0.7
4.42"
1.40"
1.91"
1.11"
1975
-1.6
4.71"
1.28"
0.36"
3.07"
1984
-0.6
9.32"
2.87"
5.09"
1.36"
1988
-1.6
9.33"
5.21"
0.64"
3.48"
1995
-0.6
7.12"
2.31"
3.36"
1.45"
1998
-1.1
6.72"
0.85"
4.61"
1.26"
1999
-1.2
5.32"
2.39"
1.43"
1.50"
2000
-0.5
5.09"
1.64"
1.04"
2.41"
2007
-1.0
6.34"
3.25"
2.88"
0.21"
2010 -1.4 11.04" 7.03"  2.08" 1.93"
 
 
SON
Sep.
Oct.
Nov.
La Niña Average
6.68"
3.00"
2.15"
1.53"
1950-2010 Longterm Average
7.35"
3.48"
2.12"
1.75"
Difference from Longterm Average
-0.67"
-0.48"
+0.03"
-0.22"
# Below
13
(68.4%)
13
(68.4%)
12
(63.2%)
12
(63.2%)
# Above
6
(31.6%)
6
(31.6%)
7
(36.8%)
7
(36.8%)
# Same
0
(0%)
0
(0%)
0
(0%)
0
(0%)

Rochester, MN

In Rochester, MN, there has been a nearly even split of La Niña autumns being drier (10) and wetter (9) than the 1950-2010 average of 7.01 inches. The overall average for these autumns is 7.13 inches, and they have ranged from 2.66 inches (1999) to 13.60 inches (2010).

The table below provides a monthly break down of autumn precipitation in Rochester, MN during La Niña.
Rochester, MN Precipitation during La Nina Autumns
La Niña Autumn
Precipitation
in Rochester, MN
Breakdown of Monthly Precipitation in Rochester, MN during La Niña Autumns
Year
Autumn
(SON)
ONI
Precipitation
Autumn
(SON)
Sep.
Oct.
Nov.
1950
-0.9
3.32" 1.71" 0.83" 0.78"
1954
-1.1
7.14" 3.48" 2.76" 0.90"
1955
-1.8
3.27" 1.33" 1.42" 0.52"
1956
-0.9
4.45" 0.83" 2.26" 1.36"
1962
-0.6
4.01" 1.88" 1.95" 0.18"
1964
-1.2
8.87" 5.99" 0.52" 2.36"
1970
-0.8
12.21" 4.09" 6.08" 2.04"
1971
-0.9
9.48" 3.93" 3.37" 2.18"
1973
-1.7
11.81" 5.84" 2.60" 3.37"
1974
-0.7
4.41" 1.01" 2.54" 0.86"
1975
-1.6
5.67" 0.38" 0.68" 4.61"
1984
-0.6
7.86" 2.40" 3.78" 1.68"
1988
-1.6
7.04" 3.77" 0.40" 2.87"
1995
-0.6
6.09" 2.34" 3.07" 0.68"
1998
-1.1
6.90" 1.04" 4.71" 1.15"
1999
-1.2
2.66" 0.74" 0.92" 1.00"
2000
-0.5
5.75" 1.04" 1.65" 3.06"
2007
-1.0
10.98" 7.40" 3.40" 0.18"
2010 -1.4 13.60" 9.95" 0.79" 2.86"
 
 
SON
Sep.
Oct.
Nov.
La Niña Average
7.13"
3.11"
2.30"
1.72"
1950-2010 Longterm Average
7.01"
3.18"
2.16"
1.67"
Difference from Longterm Average
+0.12"
-0.07"
+0.14"
+0.05"
# Below
10
(52.6%)
11
(57.9%)
9
(47.4%)
10
(52.6%)
# Above
9
(47.4%)
8
(42.1%)
10
(52.6%)
9
(47.4%)
# Same
0
(0%)
0
(0%)
0
(0%)
0
(0%)

Autumn Snowfall in the Upper Mississippi River Valley

La Niña autumns usually have less snow than normal across the Upper Mississippi River Valley.  More details on the snowfall at La Crosse, WI and Rochester, MN can be found below.

La Crosse, WI

At La Crosse, WI, La Niña autumns usually have less snow than normal (13 out of 19, 68.4%).  The average autumn snowfall was 3.3 inches, which was 1.2 inches less than the 1950-2010 averagel of 4.5 inches.  This below-normal snowfall tendency shows up in all three of the autumn months.  The lack of snow is not that surprising considering La Niña autumns are usually warmer and drier than normal. 

While autumn snowfall during La Niñas is usually below normal, they have varied dramatically from just a trace of snow to 7.6 inches.

The table below provides a monthly break down of autumn snowfall in La Crosse, WI during La Niña.

La Crosse, WI Snowfall during La Nina Autumns
La Niña Autumn
Snowfall
in La Crosse, WI
Breakdown of Monthly Snowfall in La Crosse, WI during La Niña Autumns
Year
Autumn
(SON)
ONI
Snowfall
Autumn
(SON)
Sep.
Oct.
Nov.
1950
-0.9
1.4" 0.0" 0.0" 1.4"
1954
-1.1
6.7" 0.0" T 6.7"
1955
-1.8
4.8" 0.0" T 4.8"
1956
-0.9
6.7" 0.0" 0.0" 6.7"
1962
-0.6
0.2" 0.0" T 0.2"
1964
-1.2
4.7" 0.0" T 4.7"
1970
-0.8
1.1" 0.0" T 1.1"
1971
-0.9
3.8" 0.0" 0.0" 3.8"
1973
-1.7
T 0.0" 0.0" T
1974
-0.7
2.2"  T 0.0" 2.2"
1975
-1.6
1.7" 0.0" 0.0" 1.7"
1984
-0.6
2.9" 0.0" T 2.9"
1988
-1.6
7.6" 0.0" T 7.6"
1995
-0.6
6.6" 0.0" 0.5" 6.1"
1998
-1.1
0.3" 0.0" 0.0" 0.3"
1999
-1.2
0.3" 0.0" 0.3" 0.3"
2000
-0.5
2.8" 0.0" T 2.8"
2007
-1.0
1.7" 0.0" 0.0" 1.7"
2010 -1.4  T 0.0"
0.0" T
 
 
SON
Sep.
Oct.
Nov.
La Niña Average
3.3"
0.0"
0.1"
3.2"
1950-2010 Longterm Average
4.5"
0.0"
0.2"
4.3"
Difference from Longterm Average
-1.2"
0.0"
-0.1"
-1.1"
# Below
13
(100%)
19
(100%)
17
(89.5%)
13
(68.4%)
# Above
6
(0%)
0
(0.0%)
2
(10.5%)
6
(31.6%)
# Same
0
(0%)
0
(0%)
0
(0%)
0
(0%)

Rochester, MN

At Rochester, MN, La Niña autumns usually have less snow than normal (13 out of 19, 68.4%).  The average autumn snowfall was 4.8 inches, which was 1.5 inches less than the 1950-2010 average of 6.3 inches.  The below normal snowfall tendency shows up in all three of the autumn months.  The lack of snow is not that surprising considering La Niña autumns are usually warmer than normal.

While autumn snowfall during La Niñas is typically below normal, they have varied dramatically from just a trace to 10.8 inches.

The table below provides a monthly break down of autumn snowfall in Rochester, MN during La Niña.

Rochester, MN Snowfall during La Nina Autumns
La Niña Autumn
Snowfall
in Rochester, MN
Breakdown of Monthly Snowfall in Rochester, MN during La Niña Autumns
Year
Autumn
(SON)
ONI
Snowfall
Autumn
(SON)
Sep.
Oct.
Nov.
1950
-0.9
 1.4"  0.0" 0.0" 1.4"
1954
-1.1
 8.0"  0.0" 0.8"  7.2"
1955
-1.8
 5.0"  0.0" 0.7"  4.3"
1956
-0.9
 6.1"  0.0" 0.0"  6.1"
1962
-0.6
 0.2"  0.0" 0.2"  0.2"
1964
-1.2
 4.8"  0.0" T  4.8"
1970
-0.8
 7.6"  0.0" 0.1"  7.6"
1971
-0.9
 7.8"  0.0" 0.0"  7.8"
1973
-1.7
 0.3"  0.0" T  0.3"
1974
-0.7
 2.9"  0.0" 0.0"  2.9"
1975
-1.6
 7.8"  0.0" T  7.8"
1984
-0.6
 3.7" 0.0" T  3.7"
1988
-1.6
 10.8"  0.0" T  10.8"
1995
-0.6
6.3"  T  2.3"  4.0"
1998
-1.1
 2.0" 0.0" 0.0"  2.0"
1999
-1.2
 T  0.0" 0.5"  T
2000
-0.5
 5.4"  0.0" T  5.4"
2007
-1.0
 0.9"  0.0" 0.0"  0.9"
2010 -1.4 1.3"  0.0" 0.0" 1.3"
 
 
SON
Sep.
Oct.
Nov.
La Niña Average
4.8"
0.0"
0.4"
4.4"
1950-2010 Longterm Average
6.3"
0.0"
1.0"
5.3"
Difference from Longterm Average
-1.5"
0.0"
-0.6"
-0.9"
# Below
13
(68.4%)
19
(100%)
18
(94.7%)
12
(63.2%)
# Above
5
(26.3%)
0
(0.0%)
1
(5.3%)
7
(36.8%)
# Same
 1
(5.3%)
 0
(0%)
0
(0%)
0
(0%)

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