Data / Cooling degree days / Illinois

Cooling degree days in Illinois

Cooling degree days in Illinois was 1,038 degree days (base 65°F) in 2025, according to NOAA National Centers for Environmental Information. That is up 1.4% from 2024. That is the 23rd highest of 48 states in 2025.

2025, degree days (base 65°F)1,038
Change on 2024+1.4%
Rank23rd of 48US states ranked
Series high1,2231936
Series low4801915

Next release: Wednesday, 6 October 2027, estimated by Invokely from past publication dates (low confidence), not announced by the publisher. Release calendar

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Cooling degree days in Illinois, 1895 to 2025

4006008001,0001,2001,400189519141933195219711990200920251895: 920 degree days (base 65°F)1896: 889 degree days (base 65°F)1897: 889 degree days (base 65°F)1898: 882 degree days (base 65°F)1899: 902 degree days (base 65°F)1900: 1,007 degree days (base 65°F)1901: 1,051 degree days (base 65°F)1902: 647 degree days (base 65°F)1903: 628 degree days (base 65°F)1904: 574 degree days (base 65°F)1905: 757 degree days (base 65°F)1906: 856 degree days (base 65°F)1907: 611 degree days (base 65°F)1908: 803 degree days (base 65°F)1909: 726 degree days (base 65°F)1910: 778 degree days (base 65°F)1911: 988 degree days (base 65°F)1912: 709 degree days (base 65°F)1913: 931 degree days (base 65°F)1914: 957 degree days (base 65°F)1915: 480 degree days (base 65°F)1916: 926 degree days (base 65°F)1917: 568 degree days (base 65°F)1918: 838 degree days (base 65°F)1919: 987 degree days (base 65°F)1920: 765 degree days (base 65°F)1921: 1,172 degree days (base 65°F)1922: 927 degree days (base 65°F)1923: 819 degree days (base 65°F)1924: 532 degree days (base 65°F)1925: 923 degree days (base 65°F)1926: 723 degree days (base 65°F)1927: 616 degree days (base 65°F)1928: 686 degree days (base 65°F)1929: 642 degree days (base 65°F)1930: 925 degree days (base 65°F)1931: 1,066 degree days (base 65°F)1932: 889 degree days (base 65°F)1933: 1,100 degree days (base 65°F)1934: 1,179 degree days (base 65°F)1935: 813 degree days (base 65°F)1936: 1,223 degree days (base 65°F)1937: 871 degree days (base 65°F)1938: 883 degree days (base 65°F)1939: 973 degree days (base 65°F)1940: 828 degree days (base 65°F)1941: 975 degree days (base 65°F)1942: 779 degree days (base 65°F)1943: 901 degree days (base 65°F)1944: 993 degree days (base 65°F)1945: 609 degree days (base 65°F)1946: 736 degree days (base 65°F)1947: 925 degree days (base 65°F)1948: 810 degree days (base 65°F)1949: 961 degree days (base 65°F)1950: 613 degree days (base 65°F)1951: 616 degree days (base 65°F)1952: 925 degree days (base 65°F)1953: 986 degree days (base 65°F)1954: 961 degree days (base 65°F)1955: 1,059 degree days (base 65°F)1956: 836 degree days (base 65°F)1957: 802 degree days (base 65°F)1958: 666 degree days (base 65°F)1959: 1,028 degree days (base 65°F)1960: 773 degree days (base 65°F)1961: 761 degree days (base 65°F)1962: 794 degree days (base 65°F)1963: 824 degree days (base 65°F)1964: 881 degree days (base 65°F)1965: 763 degree days (base 65°F)1966: 773 degree days (base 65°F)1967: 560 degree days (base 65°F)1968: 797 degree days (base 65°F)1969: 744 degree days (base 65°F)1970: 876 degree days (base 65°F)1971: 857 degree days (base 65°F)1972: 722 degree days (base 65°F)1973: 907 degree days (base 65°F)1974: 673 degree days (base 65°F)1975: 845 degree days (base 65°F)1976: 703 degree days (base 65°F)1977: 925 degree days (base 65°F)1978: 858 degree days (base 65°F)1979: 739 degree days (base 65°F)1980: 954 degree days (base 65°F)1981: 733 degree days (base 65°F)1982: 723 degree days (base 65°F)1983: 1,081 degree days (base 65°F)1984: 839 degree days (base 65°F)1985: 743 degree days (base 65°F)1986: 859 degree days (base 65°F)1987: 1,059 degree days (base 65°F)1988: 1,160 degree days (base 65°F)1989: 737 degree days (base 65°F)1990: 762 degree days (base 65°F)1991: 1,101 degree days (base 65°F)1992: 512 degree days (base 65°F)1993: 804 degree days (base 65°F)1994: 746 degree days (base 65°F)1995: 1,040 degree days (base 65°F)1996: 694 degree days (base 65°F)1997: 698 degree days (base 65°F)1998: 1,028 degree days (base 65°F)1999: 936 degree days (base 65°F)2000: 806 degree days (base 65°F)2001: 876 degree days (base 65°F)2002: 1,020 degree days (base 65°F)2003: 752 degree days (base 65°F)2004: 679 degree days (base 65°F)2005: 1,108 degree days (base 65°F)2006: 870 degree days (base 65°F)2007: 1,052 degree days (base 65°F)2008: 792 degree days (base 65°F)2009: 623 degree days (base 65°F)2010: 1,113 degree days (base 65°F)2011: 982 degree days (base 65°F)2012: 1,156 degree days (base 65°F)2013: 805 degree days (base 65°F)2014: 725 degree days (base 65°F)2015: 842 degree days (base 65°F)2016: 1,089 degree days (base 65°F)2017: 840 degree days (base 65°F)2018: 1,096 degree days (base 65°F)2019: 936 degree days (base 65°F)2020: 951 degree days (base 65°F)2021: 1,063 degree days (base 65°F)2022: 929 degree days (base 65°F)2023: 881 degree days (base 65°F)2024: 1,024 degree days (base 65°F)2025: 1,038 degree days (base 65°F)
degree days (base 65°F). Source: NOAA NCEI, NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide. Retrieved 2026-10-12, published 2026-10-06.
All 131 values
Perioddegree days (base 65°F)
20251,038
20241,024
2023881
2022929
20211,063
2020951
2019936
20181,096
2017840
20161,089
2015842
2014725
2013805
20121,156
2011982
20101,113
2009623
2008792
20071,052
2006870
20051,108
2004679
2003752
20021,020
2001876
2000806
1999936
19981,028
1997698
1996694
19951,040
1994746
1993804
1992512
19911,101
1990762
1989737
19881,160
19871,059
1986859
1985743
1984839
19831,081
1982723
1981733
1980954
1979739
1978858
1977925
1976703
1975845
1974673
1973907
1972722
1971857
1970876
1969744
1968797
1967560
1966773
1965763
1964881
1963824
1962794
1961761
1960773
19591,028
1958666
1957802
1956836
19551,059
1954961
1953986
1952925
1951616
1950613
1949961
1948810
1947925
1946736
1945609
1944993
1943901
1942779
1941975
1940828
1939973
1938883
1937871
19361,223
1935813
19341,179
19331,100
1932889
19311,066
1930925
1929642
1928686
1927616
1926723
1925923
1924532
1923819
1922927
19211,172
1920765
1919987
1918838
1917568
1916926
1915480
1914957
1913931
1912709
1911988
1910778
1909726
1908803
1907611
1906856
1905757
1904574
1903628
1902647
19011,051
19001,007
1899902
1898882
1897889
1896889
1895920

Compared with United States

Place2025
Illinois1,038
United States1,502

Rankings

Definition

Sum over January to December of the degrees by which the daily mean temperature exceeds 65°F, a measure of cooling demand. NOAA estimates monthly values from nClimDiv temperatures and weights areas by population (2010 Census).

NOAA publishes these for operational monitoring; they can differ from official degree day publications.

How to cite

NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide. From the NOAA Monthly U.S. Climate Divisional Database (nClimDiv), doi:10.7289/V5M32STR. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

NOAA National Centers for Environmental Information. (2026). NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide (Cooling degree days, Illinois, 1895 to 2025) [Data set]. Retrieved October 12, 2026, from https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json

MLA 9

NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide, Cooling degree days, Illinois, 1895 to 2025. NOAA National Centers for Environmental Information, 6 Oct. 2026, https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json. Invokely, https://invokely.ai/en/cooling-degree-days/illinois. Accessed 12 Oct. 2026.

Chicago (author-date)

NOAA National Centers for Environmental Information. 2026. NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide. Cooling degree days, Illinois, 1895 to 2025. Dataset. Accessed October 12, 2026. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json. Also distributed by Invokely, https://invokely.ai/en/cooling-degree-days/illinois.

Harvard

NOAA National Centers for Environmental Information (2026) NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide, Cooling degree days, Illinois, 1895 to 2025 [Dataset]. Available at: https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json, via Invokely: https://invokely.ai/en/cooling-degree-days/illinois (Accessed: 12 October 2026).

BibTeX
@misc{noaa_cooling_degree_days_illinois_2025,
  author = {{NOAA National Centers for Environmental Information}},
  title = {{NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide: Cooling degree days, Illinois, 1895 to 2025}},
  year = {2026},
  howpublished = {Data set},
  url = {https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/en/cooling-degree-days/illinois. Publisher attribution: NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide. From the NOAA Monthly U.S. Climate Divisional Database (nClimDiv), doi:10.7289/V5M32STR. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - NOAA National Centers for Environmental Information
TI  - NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide: Cooling degree days, Illinois, 1895 to 2025
PY  - 2026
DA  - 2026/10/06
PB  - NOAA National Centers for Environmental Information
DB  - Invokely
UR  - https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json
L2  - https://invokely.ai/en/cooling-degree-days/illinois
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/cooling-degree-days/illinois.
N1  - Publisher attribution: NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide. From the NOAA Monthly U.S. Climate Divisional Database (nClimDiv), doi:10.7289/V5M32STR. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/cdd/12/12/1895-2025/data.json. Retrieved 2026-10-12.
ER  -
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Questions

What is the cooling degree days in Illinois?

Cooling degree days in Illinois was 1,038 degree days (base 65°F) in 2025, according to NOAA National Centers for Environmental Information. That is up 1.4% from 2024. That is the 23rd highest of 48 states in 2025.

Where does this figure come from?

NOAA National Centers for Environmental Information. NOAA Climate at a Glance, January to December cooling degree days (base 65°F), contiguous US and statewide. Retrieved by Invokely on 2026-10-12.

What was the highest cooling degree days in Illinois?

1,223 degree days (base 65°F) in 1936, the highest value since 1895 in this series.

Cooling degree days elsewhere in United States

Related statistics for Illinois

All statistics for Illinois | Illinois in figures