Data / Heating degree days / Illinois

Heating degree days in Illinois

Heating degree days in Illinois was 5,896 degree days (base 65°F) in 2025, according to NOAA National Centers for Environmental Information. That is up 16.1% from 2024. That is the 17th highest of 48 states in 2025.

2025, degree days (base 65°F)5,896
Change on 2024+16.1%
Rank17th of 48US states ranked
Series high7,5191917
Series low5,0802024

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Heating degree days in Illinois, 1895 to 2025

5,0005,5006,0006,5007,0007,5008,000189519141933195219711990200920251895: 7,214 degree days (base 65°F)1896: 6,264 degree days (base 65°F)1897: 6,551 degree days (base 65°F)1898: 6,533 degree days (base 65°F)1899: 6,613 degree days (base 65°F)1900: 6,378 degree days (base 65°F)1901: 6,978 degree days (base 65°F)1902: 6,567 degree days (base 65°F)1903: 6,803 degree days (base 65°F)1904: 7,271 degree days (base 65°F)1905: 6,856 degree days (base 65°F)1906: 6,421 degree days (base 65°F)1907: 6,745 degree days (base 65°F)1908: 6,210 degree days (base 65°F)1909: 6,703 degree days (base 65°F)1910: 6,602 degree days (base 65°F)1911: 6,247 degree days (base 65°F)1912: 7,210 degree days (base 65°F)1913: 6,198 degree days (base 65°F)1914: 6,510 degree days (base 65°F)1915: 6,483 degree days (base 65°F)1916: 6,768 degree days (base 65°F)1917: 7,519 degree days (base 65°F)1918: 6,586 degree days (base 65°F)1919: 6,465 degree days (base 65°F)1920: 6,667 degree days (base 65°F)1921: 5,511 degree days (base 65°F)1922: 6,054 degree days (base 65°F)1923: 6,446 degree days (base 65°F)1924: 7,121 degree days (base 65°F)1925: 6,669 degree days (base 65°F)1926: 7,010 degree days (base 65°F)1927: 6,141 degree days (base 65°F)1928: 6,369 degree days (base 65°F)1929: 6,990 degree days (base 65°F)1930: 6,318 degree days (base 65°F)1931: 5,468 degree days (base 65°F)1932: 6,427 degree days (base 65°F)1933: 6,121 degree days (base 65°F)1934: 6,256 degree days (base 65°F)1935: 6,643 degree days (base 65°F)1936: 6,939 degree days (base 65°F)1937: 6,909 degree days (base 65°F)1938: 5,739 degree days (base 65°F)1939: 5,949 degree days (base 65°F)1940: 6,884 degree days (base 65°F)1941: 5,968 degree days (base 65°F)1942: 6,406 degree days (base 65°F)1943: 6,855 degree days (base 65°F)1944: 6,377 degree days (base 65°F)1945: 6,647 degree days (base 65°F)1946: 5,640 degree days (base 65°F)1947: 6,688 degree days (base 65°F)1948: 6,486 degree days (base 65°F)1949: 6,169 degree days (base 65°F)1950: 6,982 degree days (base 65°F)1951: 6,968 degree days (base 65°F)1952: 6,241 degree days (base 65°F)1953: 5,884 degree days (base 65°F)1954: 5,971 degree days (base 65°F)1955: 6,382 degree days (base 65°F)1956: 6,107 degree days (base 65°F)1957: 6,429 degree days (base 65°F)1958: 6,795 degree days (base 65°F)1959: 6,591 degree days (base 65°F)1960: 6,791 degree days (base 65°F)1961: 6,482 degree days (base 65°F)1962: 6,740 degree days (base 65°F)1963: 6,808 degree days (base 65°F)1964: 6,149 degree days (base 65°F)1965: 6,351 degree days (base 65°F)1966: 6,721 degree days (base 65°F)1967: 6,610 degree days (base 65°F)1968: 6,389 degree days (base 65°F)1969: 6,763 degree days (base 65°F)1970: 6,587 degree days (base 65°F)1971: 6,244 degree days (base 65°F)1972: 6,955 degree days (base 65°F)1973: 5,882 degree days (base 65°F)1974: 6,282 degree days (base 65°F)1975: 6,252 degree days (base 65°F)1976: 6,825 degree days (base 65°F)1977: 6,560 degree days (base 65°F)1978: 7,132 degree days (base 65°F)1979: 7,093 degree days (base 65°F)1980: 6,711 degree days (base 65°F)1981: 6,295 degree days (base 65°F)1982: 6,654 degree days (base 65°F)1983: 6,447 degree days (base 65°F)1984: 6,340 degree days (base 65°F)1985: 6,654 degree days (base 65°F)1986: 6,050 degree days (base 65°F)1987: 5,665 degree days (base 65°F)1988: 6,493 degree days (base 65°F)1989: 6,766 degree days (base 65°F)1990: 5,617 degree days (base 65°F)1991: 5,920 degree days (base 65°F)1992: 6,110 degree days (base 65°F)1993: 6,587 degree days (base 65°F)1994: 6,195 degree days (base 65°F)1995: 6,588 degree days (base 65°F)1996: 6,893 degree days (base 65°F)1997: 6,531 degree days (base 65°F)1998: 5,167 degree days (base 65°F)1999: 5,824 degree days (base 65°F)2000: 6,130 degree days (base 65°F)2001: 5,740 degree days (base 65°F)2002: 6,002 degree days (base 65°F)2003: 6,287 degree days (base 65°F)2004: 5,918 degree days (base 65°F)2005: 5,931 degree days (base 65°F)2006: 5,535 degree days (base 65°F)2007: 5,940 degree days (base 65°F)2008: 6,652 degree days (base 65°F)2009: 6,396 degree days (base 65°F)2010: 6,105 degree days (base 65°F)2011: 6,043 degree days (base 65°F)2012: 5,148 degree days (base 65°F)2013: 6,612 degree days (base 65°F)2014: 7,164 degree days (base 65°F)2015: 6,004 degree days (base 65°F)2016: 5,544 degree days (base 65°F)2017: 5,543 degree days (base 65°F)2018: 6,427 degree days (base 65°F)2019: 6,430 degree days (base 65°F)2020: 5,774 degree days (base 65°F)2021: 5,684 degree days (base 65°F)2022: 6,325 degree days (base 65°F)2023: 5,320 degree days (base 65°F)2024: 5,080 degree days (base 65°F)2025: 5,896 degree days (base 65°F)
degree days (base 65°F). Source: NOAA NCEI, NOAA Climate at a Glance, January to December heating 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)
20255,896
20245,080
20235,320
20226,325
20215,684
20205,774
20196,430
20186,427
20175,543
20165,544
20156,004
20147,164
20136,612
20125,148
20116,043
20106,105
20096,396
20086,652
20075,940
20065,535
20055,931
20045,918
20036,287
20026,002
20015,740
20006,130
19995,824
19985,167
19976,531
19966,893
19956,588
19946,195
19936,587
19926,110
19915,920
19905,617
19896,766
19886,493
19875,665
19866,050
19856,654
19846,340
19836,447
19826,654
19816,295
19806,711
19797,093
19787,132
19776,560
19766,825
19756,252
19746,282
19735,882
19726,955
19716,244
19706,587
19696,763
19686,389
19676,610
19666,721
19656,351
19646,149
19636,808
19626,740
19616,482
19606,791
19596,591
19586,795
19576,429
19566,107
19556,382
19545,971
19535,884
19526,241
19516,968
19506,982
19496,169
19486,486
19476,688
19465,640
19456,647
19446,377
19436,855
19426,406
19415,968
19406,884
19395,949
19385,739
19376,909
19366,939
19356,643
19346,256
19336,121
19326,427
19315,468
19306,318
19296,990
19286,369
19276,141
19267,010
19256,669
19247,121
19236,446
19226,054
19215,511
19206,667
19196,465
19186,586
19177,519
19166,768
19156,483
19146,510
19136,198
19127,210
19116,247
19106,602
19096,703
19086,210
19076,745
19066,421
19056,856
19047,271
19036,803
19026,567
19016,978
19006,378
18996,613
18986,533
18976,551
18966,264
18957,214

Compared with United States

Place2025
Illinois5,896
United States4,062

Rankings

Definition

Sum over January to December of the degrees by which the daily mean temperature falls below 65°F, a measure of heating 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 heating 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/hdd/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 heating degree days (base 65°F), contiguous US and statewide (Heating 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/hdd/12/12/1895-2025/data.json

MLA 9

NOAA Climate at a Glance, January to December heating degree days (base 65°F), contiguous US and statewide, Heating 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/hdd/12/12/1895-2025/data.json. Invokely, https://invokely.ai/en/heating-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 heating degree days (base 65°F), contiguous US and statewide. Heating 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/hdd/12/12/1895-2025/data.json. Also distributed by Invokely, https://invokely.ai/en/heating-degree-days/illinois.

Harvard

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

BibTeX
@misc{noaa_heating_degree_days_illinois_2025,
  author = {{NOAA National Centers for Environmental Information}},
  title = {{NOAA Climate at a Glance, January to December heating degree days (base 65°F), contiguous US and statewide: Heating 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/hdd/12/12/1895-2025/data.json},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/en/heating-degree-days/illinois. Publisher attribution: NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December heating 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/hdd/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 heating degree days (base 65°F), contiguous US and statewide: Heating 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/hdd/12/12/1895-2025/data.json
L2  - https://invokely.ai/en/heating-degree-days/illinois
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/en/heating-degree-days/illinois.
N1  - Publisher attribution: NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December heating 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/hdd/12/12/1895-2025/data.json. Retrieved 2026-10-12.
ER  -
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Questions

What is the heating degree days in Illinois?

Heating degree days in Illinois was 5,896 degree days (base 65°F) in 2025, according to NOAA National Centers for Environmental Information. That is up 16.1% from 2024. That is the 17th 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 heating degree days (base 65°F), contiguous US and statewide. Retrieved by Invokely on 2026-10-12.

What was the highest heating degree days in Illinois?

7,519 degree days (base 65°F) in 1917, the highest value since 1895 in this series.

Heating degree days elsewhere in United States

Related statistics for Illinois

All statistics for Illinois | Illinois in figures