# Heating degree days in Illinois

Heating degree days in Illinois was 5,896 degree days (base 65°F) in 2025. Source: NOAA National Centers for Environmental Information.

- Indicator id: `heating_degree_days_annual`
- Place id: `us-state-17`
- Unit: degree days (base 65°F)
- 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).
- Note: NOAA publishes these for operational monitoring; they can differ from official degree day publications.
- Source: NOAA National Centers for Environmental Information, NOAA Climate at a Glance, January to December heating degree days (base 65°F), contiguous US and statewide (https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/time-series/11/hdd/12/12/1895-2025/data.json)
- Publisher page: https://invokely.ai/en/publishers/noaa-ncei
- Retrieved: 2026-10-12
- License: Public domain (US government work); NCEI asks users to cite the nClimDiv dataset
- Citation: 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.
- Web page: https://invokely.ai/en/heating-degree-days/illinois
- API: https://invokely.ai/api/v1/series?indicator=heating_degree_days_annual&place=us-state-17

| Period | degree days (base 65°F) |
|---|---:|
| 2025 | 5,896 |
| 2024 | 5,080 |
| 2023 | 5,320 |
| 2022 | 6,325 |
| 2021 | 5,684 |
| 2020 | 5,774 |
| 2019 | 6,430 |
| 2018 | 6,427 |
| 2017 | 5,543 |
| 2016 | 5,544 |
| 2015 | 6,004 |
| 2014 | 7,164 |
| 2013 | 6,612 |
| 2012 | 5,148 |
| 2011 | 6,043 |
| 2010 | 6,105 |
| 2009 | 6,396 |
| 2008 | 6,652 |
| 2007 | 5,940 |
| 2006 | 5,535 |
| 2005 | 5,931 |
| 2004 | 5,918 |
| 2003 | 6,287 |
| 2002 | 6,002 |
| 2001 | 5,740 |
| 2000 | 6,130 |
| 1999 | 5,824 |
| 1998 | 5,167 |
| 1997 | 6,531 |
| 1996 | 6,893 |
| 1995 | 6,588 |
| 1994 | 6,195 |
| 1993 | 6,587 |
| 1992 | 6,110 |
| 1991 | 5,920 |
| 1990 | 5,617 |
| 1989 | 6,766 |
| 1988 | 6,493 |
| 1987 | 5,665 |
| 1986 | 6,050 |
| 1985 | 6,654 |
| 1984 | 6,340 |
| 1983 | 6,447 |
| 1982 | 6,654 |
| 1981 | 6,295 |
| 1980 | 6,711 |
| 1979 | 7,093 |
| 1978 | 7,132 |
| 1977 | 6,560 |
| 1976 | 6,825 |
| 1975 | 6,252 |
| 1974 | 6,282 |
| 1973 | 5,882 |
| 1972 | 6,955 |
| 1971 | 6,244 |
| 1970 | 6,587 |
| 1969 | 6,763 |
| 1968 | 6,389 |
| 1967 | 6,610 |
| 1966 | 6,721 |
| 1965 | 6,351 |
| 1964 | 6,149 |
| 1963 | 6,808 |
| 1962 | 6,740 |
| 1961 | 6,482 |
| 1960 | 6,791 |
| 1959 | 6,591 |
| 1958 | 6,795 |
| 1957 | 6,429 |
| 1956 | 6,107 |
| 1955 | 6,382 |
| 1954 | 5,971 |
| 1953 | 5,884 |
| 1952 | 6,241 |
| 1951 | 6,968 |
| 1950 | 6,982 |
| 1949 | 6,169 |
| 1948 | 6,486 |
| 1947 | 6,688 |
| 1946 | 5,640 |
| 1945 | 6,647 |
| 1944 | 6,377 |
| 1943 | 6,855 |
| 1942 | 6,406 |
| 1941 | 5,968 |
| 1940 | 6,884 |
| 1939 | 5,949 |
| 1938 | 5,739 |
| 1937 | 6,909 |
| 1936 | 6,939 |
| 1935 | 6,643 |
| 1934 | 6,256 |
| 1933 | 6,121 |
| 1932 | 6,427 |
| 1931 | 5,468 |
| 1930 | 6,318 |
| 1929 | 6,990 |
| 1928 | 6,369 |
| 1927 | 6,141 |
| 1926 | 7,010 |
| 1925 | 6,669 |
| 1924 | 7,121 |
| 1923 | 6,446 |
| 1922 | 6,054 |
| 1921 | 5,511 |
| 1920 | 6,667 |
| 1919 | 6,465 |
| 1918 | 6,586 |
| 1917 | 7,519 |
| 1916 | 6,768 |
| 1915 | 6,483 |
| 1914 | 6,510 |
| 1913 | 6,198 |
| 1912 | 7,210 |
| 1911 | 6,247 |
| 1910 | 6,602 |
| 1909 | 6,703 |
| 1908 | 6,210 |
| 1907 | 6,745 |
| 1906 | 6,421 |
| 1905 | 6,856 |
| 1904 | 7,271 |
| 1903 | 6,803 |
| 1902 | 6,567 |
| 1901 | 6,978 |
| 1900 | 6,378 |
| 1899 | 6,613 |
| 1898 | 6,533 |
| 1897 | 6,551 |
| 1896 | 6,264 |
| 1895 | 7,214 |