New 1981-2010 Climate Normals Start Aug 1

The National Climatic Data Center (NCDC) is responsible for producing 30 year climate normals of numerous climatological variables every 10 years for U.S. locations. The primary variables include temperature, precipitation, and derived products such as heating and cooling degree days. Normals serve as a baseline average of important climate variables that are used to understand average climate conditions at any location and serve as a consistent point of reference.

In this latest set of normals (1981-2010), the 1971-1980 decade was removed (generally considered a cool decade) and the 2001-2010 decade was added (warmer by comparison). As a result, the 1981-2010 average temperature across the United States is now approximately 0.5 F degrees warmer than the 1971-2000 period. However, this warming is not uniform across the country or from season to season. For instance, the 1981-2010 average high temperature for the mid section of the U.S. is cooler in July compared to the previous set of normals. Meanwhile, the January normal lows are much warmer across the Northern Plains and Upper Mississippi River Valley compared to 1971-2000. The graphics below illustrate the changes, along with the overall warming by state from the old set of normals to the new set.

change in normals
change in normals by state

Below is a comparison of how the 1971-2000 (Old) normals compare to the 1981-2010 (New) normals for Chicago, IL (O'Hare) and Rockford, IL..

Old is the 1971-2000 normals. New is the 1981-2010 normals. Red text indicated a warmer temperature compared to the old set of normals. Blue text indicates cooler temperatures compared to the previous normals. Green text indicated more precipitation, while Brown text indicates less.

Chicago Jan Feb Mar Apr May Jun
  Old New Old New Old New Old New Old New Old New
High Temp

29.6

31.0

34.7

35.3

46.1

46.6

58.0

59.0

69.9

70.0

79.2

79.7

Low Temp

14.3

16.5

19.2

20.1

28.5

29.2

37.6

38.8

47.5

48.3

57.2

58.1

Ave Temp

22.0

23.8

27.0

27.7

37.3

37.9

47.8

48.9

58.7

59.1

68.2

68.9

Precipitation

1.75"

1.73"

1.63"

1.79"

2.65"

2.50"

3.68"

3.38"

3.38"

3.68"

3.63"

3.45"

Snowfall

11.3"

10.8"

8.3"

9.1"

6.0"

5.6"

1.6"

1.2"

T

T

0

0

  Jul Aug Sep Oct Nov Dec Year
  Old New Old New Old New Old New Old New Old New Old New
High Temp

83.5

84.1

81.2

81.9

73.9

74.8

62.1

62.3

47.1

48.2

34.4

34.8

58.3

59.1

Low Temp

63.2

63.9

62.2

62.9

53.7

54.3

42.1

42.8

31.6

32.4

20.4

20.7

39.8

40.8

Ave Temp

73.3

74.0

71.7

72.4

63.8

64.6

52.1

52.5

39.3

40.3

27.4

27.7

49.1

49.9

Precipitation

3.51"

3.70"

4.62"

4.90"

3.27"

3.21"

2.71"

3.15"

3.01"

3.15"

2.43"

2.25"

36.27"

36.89"

Snowfall

0

0

0

0

0

0

0.3"

0.3"

1.8"

1.2"

8.7"

8.5"

38.0"

36.7"

 

Rockford Jan Feb Mar Apr May Jun
  Old New Old New Old New Old New Old New Old New
High Temp 27.2
29.5
33.0
34.2
45.5
46.9
59.1
60.7
71.2
71.8
79.9
81.1
Low Temp 10.8 13.5 16.3 17.7 26.7 27.5 36.8 38.1 47.9 48.4 57.6 58.5
Ave Temp 19.0 21.5 24.7 25.9 36.1 37.2 47.9 49.4 59.6 60.1 68.8 69.8
Precipitation 1.41 1.37" 1.34" 1.41" 2.39" 2.32" 3.62" 3.35" 4.03" 4.02" 4.80" 4.65"
Snowfall 10.3" 10.2" 7.9" 7.7" 5.6" 4.8" 1.4" 0.9" T T 0 0
  Jul Aug Sep Oct Nov Dec Year
  Old New Old New Old New Old New Old New Old New Old New
High Temp 83.1
84.5
80.9
82.4
73.9
75.4
61.8
62.7
45.5
47.6
32.0
33.2
57.8
59.3
Low Temp 62.6 63.0 60.9 61.3 51.8 52.4 40.1 40.7 29.0 30.3 16.9 17.7 38.1 39.2
Ave Temp 72.9 73.8 70.9 71.9 62.8 63.9 51.0 51.7 37.2 38.9 24.4 25.4 47.9 49.2
Precipitation 4.10" 3.95" 4.21" 4.59" 3.47" 3.35" 2.57" 2.67" 2.63" 2.58" 2.06" 1.98" 36.63" 36.24"
Snowfall 0 0 0 0 0 0 0.1" 0.1" 2.6" 1.7" 10.8" 11.3" 38.7" 36.7"

More details on the new climate normals will be added to this, or other news stories, over the next few weeks.

The National Weather Service will use these normals starting August 1st.


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