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Topics / Climate / United States / Illinois

Was September normal in Illinois?

September 2026 · 102 counties · data family: climatedata.dev

Much warmer than normal

73.0°FStatewide average temperature, September 2026

+6.2°F against the 1991–2020 normal of 66.8°F
1st warmest September of 132 since 1895
Of 102 counties: 102 much warmer
Furthest above normal: Pike County (+8.2°F); least: Winnebago County (+3.8°F)
Precipitation 3.01 in, 90% of normal: near normal

Every Illinois county, September 2026September 2026 was warmer than normal in every county with a figure: 102 much warmer; furthest above normal Pike County (+8.2°F), least Winnebago County (+3.8°F).Choose a county to see its answer. The colour shows how far each county was from its own 1991–2020 normal.

+4°F or more 96
+3 to +4°F 6
+1 to +2°F 0
within 1°F 0
−1 to −2°F 0

Much warmer than normal 102
Warmer than normal 0
Near normal 0
Cooler than normal 0
Much cooler than normal 0

Every September since 1895, Illinois statewideSeptember 2026 averaged 73.0°F, +6.2°F against the 1991–2020 normal: the 1st warmest September of 132 since 1895.

Show the numbers (132 rows)

Year	September average
2026	73.0°F
2025	69.2°F
2024	68.7°F
2023	68.3°F
2022	67.0°F
2021	69.6°F
2020	65.6°F
2019	71.6°F
2018	70.3°F
2017	68.8°F
2016	70.8°F
2015	70.4°F
2014	64.7°F
2013	68.6°F
2012	64.9°F
2011	63.6°F
2010	67.2°F
2009	65.9°F
2008	67.1°F
2007	69.8°F
2006	63.7°F
2005	70.7°F
2004	67.7°F
2003	64.1°F
2002	69.3°F
2001	64.4°F
2000	66.3°F
1999	65.2°F
1998	70.9°F
1997	66.3°F
1996	64.2°F
1995	63.3°F
1994	65.2°F
1993	61.6°F
1992	64.3°F
1991	66.3°F
1990	67.9°F
1989	63.3°F
1988	67.6°F
1987	66.6°F
1986	69.2°F
1985	66.7°F
1984	64.3°F
1983	67.0°F
1982	64.7°F
1981	64.5°F
1980	67.8°F
1979	65.7°F
1978	70.1°F
1977	67.4°F
1976	63.8°F
1975	61.8°F
1974	61.0°F
1973	67.6°F
1972	67.6°F
1971	69.2°F
1970	68.3°F
1969	65.4°F
1968	65.2°F
1967	62.9°F
1966	63.3°F
1965	65.9°F
1964	66.3°F
1963	66.1°F
1962	63.4°F
1961	68.1°F
1960	70.0°F
1959	67.9°F
1958	65.8°F
1957	64.2°F
1956	65.6°F
1955	68.3°F
1954	69.6°F
1953	67.6°F
1952	65.6°F
1951	62.8°F
1950	64.5°F
1949	60.4°F
1948	67.9°F
1947	67.7°F
1946	65.6°F
1945	66.0°F
1944	66.7°F
1943	62.4°F
1942	64.4°F
1941	69.1°F
1940	65.5°F
1939	71.2°F
1938	67.9°F
1937	65.3°F
1936	69.9°F
1935	66.0°F
1934	64.0°F
1933	72.2°F
1932	64.8°F
1931	72.0°F
1930	68.5°F
1929	65.0°F
1928	61.9°F
1927	69.8°F
1926	66.5°F
1925	72.2°F
1924	60.8°F
1923	65.4°F
1922	69.1°F
1921	70.3°F
1920	68.5°F
1919	68.8°F
1918	58.9°F
1917	64.1°F
1916	64.2°F
1915	67.5°F
1914	65.6°F
1913	66.2°F
1912	67.0°F
1911	68.8°F
1910	65.9°F
1909	63.9°F
1908	69.4°F
1907	64.7°F
1906	69.7°F
1905	67.3°F
1904	66.1°F
1903	64.9°F
1902	61.6°F
1901	65.7°F
1900	68.3°F
1899	64.6°F
1898	68.9°F
1897	71.3°F
1896	62.6°F
1895	69.6°F

All 102 counties, September 2026

Record rank: 1 is the warmest September on record for that county.


1	Pike	75.6°F	+8.2°F	1 of 132	Much warmer than normal
2	Calhoun	76.3°F	+8.1°F	1 of 132	Much warmer than normal
3	Randolph	77.1°F	+8.1°F	1 of 132	Much warmer than normal
4	Bond	76.3°F	+8.0°F	1 of 132	Much warmer than normal
5	Fayette	76.0°F	+8.0°F	1 of 132	Much warmer than normal
6	Greene	75.8°F	+8.0°F	1 of 132	Much warmer than normal
7	Jackson	77.0°F	+8.0°F	1 of 132	Much warmer than normal
8	Jersey	76.3°F	+8.0°F	1 of 132	Much warmer than normal
9	Marion	76.4°F	+8.0°F	1 of 132	Much warmer than normal
10	Perry	76.7°F	+8.0°F	1 of 132	Much warmer than normal
11	Clay	76.3°F	+7.9°F	1 of 132	Much warmer than normal
12	Clinton	76.7°F	+7.9°F	1 of 132	Much warmer than normal
13	Washington	76.6°F	+7.9°F	1 of 132	Much warmer than normal
14	Alexander	78.0°F	+7.8°F	1 of 132	Much warmer than normal
15	Franklin	76.6°F	+7.8°F	1 of 132	Much warmer than normal
16	Jasper	75.8°F	+7.8°F	1 of 132	Much warmer than normal
17	Pulaski	78.1°F	+7.8°F	1 of 132	Much warmer than normal
18	Scott	75.2°F	+7.8°F	1 of 132	Much warmer than normal
19	Union	77.2°F	+7.8°F	1 of 132	Much warmer than normal
20	Williamson	76.8°F	+7.8°F	1 of 132	Much warmer than normal
21	Jefferson	76.3°F	+7.7°F	1 of 132	Much warmer than normal
22	Johnson	77.3°F	+7.7°F	1 of 132	Much warmer than normal
23	Macoupin	75.4°F	+7.7°F	1 of 132	Much warmer than normal
24	Massac	78.2°F	+7.7°F	1 of 132	Much warmer than normal
25	Montgomery	75.4°F	+7.7°F	1 of 132	Much warmer than normal
26	Pope	77.6°F	+7.7°F	1 of 132	Much warmer than normal
27	Saline	77.1°F	+7.7°F	1 of 132	Much warmer than normal
28	Effingham	75.5°F	+7.6°F	1 of 132	Much warmer than normal
29	Gallatin	77.5°F	+7.6°F	1 of 132	Much warmer than normal
30	Hardin	77.6°F	+7.6°F	2 of 132	Much warmer than normal
31	Monroe	77.0°F	+7.6°F	1 of 132	Much warmer than normal
32	Richland	76.2°F	+7.6°F	1 of 132	Much warmer than normal
33	Wayne	76.6°F	+7.6°F	1 of 132	Much warmer than normal
34	Edwards	76.8°F	+7.5°F	1 of 132	Much warmer than normal
35	Hamilton	76.6°F	+7.5°F	1 of 132	Much warmer than normal
36	White	77.1°F	+7.5°F	1 of 132	Much warmer than normal
37	Cumberland	75.1°F	+7.4°F	1 of 132	Much warmer than normal
38	Morgan	74.5°F	+7.4°F	1 of 132	Much warmer than normal
39	St. Clair	76.8°F	+7.4°F	1 of 132	Much warmer than normal
40	Crawford	75.5°F	+7.3°F	1 of 132	Much warmer than normal
41	Madison	76.2°F	+7.3°F	1 of 132	Much warmer than normal
42	Wabash	76.6°F	+7.3°F	1 of 132	Much warmer than normal
43	Brown	74.0°F	+7.2°F	1 of 132	Much warmer than normal
44	Cass	74.2°F	+7.2°F	1 of 132	Much warmer than normal
45	Lawrence	76.0°F	+7.2°F	1 of 132	Much warmer than normal
46	Shelby	74.8°F	+7.2°F	1 of 132	Much warmer than normal
47	Christian	74.6°F	+7.1°F	1 of 132	Much warmer than normal
48	Clark	74.7°F	+7.1°F	1 of 132	Much warmer than normal
49	Coles	74.4°F	+7.1°F	1 of 132	Much warmer than normal
50	Adams	74.0°F	+6.9°F	1 of 132	Much warmer than normal
51	Moultrie	74.1°F	+6.8°F	1 of 132	Much warmer than normal
52	Schuyler	73.3°F	+6.7°F	1 of 132	Much warmer than normal
53	Douglas	73.8°F	+6.6°F	1 of 132	Much warmer than normal
54	Edgar	73.5°F	+6.6°F	1 of 132	Much warmer than normal
55	Sangamon	73.7°F	+6.6°F	1 of 132	Much warmer than normal
56	Macon	73.5°F	+6.4°F	1 of 132	Much warmer than normal
57	Menard	73.3°F	+6.4°F	1 of 132	Much warmer than normal
58	Piatt	73.2°F	+6.3°F	1 of 132	Much warmer than normal
59	De Witt	72.6°F	+6.1°F	1 of 132	Much warmer than normal
60	Mason	73.0°F	+6.1°F	1 of 132	Much warmer than normal
61	McLean	72.1°F	+6.1°F	1 of 132	Much warmer than normal
62	Logan	72.7°F	+6.0°F	1 of 132	Much warmer than normal
63	Champaign	72.5°F	+5.9°F	1 of 132	Much warmer than normal
64	Mercer	71.3°F	+5.9°F	1 of 132	Much warmer than normal
65	Hancock	72.6°F	+5.8°F	3 of 132	Much warmer than normal
66	Fulton	72.0°F	+5.7°F	3 of 132	Much warmer than normal
67	Woodford	71.6°F	+5.7°F	1 of 132	Much warmer than normal
68	Ford	71.4°F	+5.5°F	1 of 132	Much warmer than normal
69	Henderson	71.6°F	+5.5°F	4 of 132	Much warmer than normal
70	McDonough	71.7°F	+5.5°F	4 of 132	Much warmer than normal
71	Stark	70.5°F	+5.5°F	2 of 132	Much warmer than normal
72	Tazewell	72.0°F	+5.5°F	1 of 132	Much warmer than normal
73	Vermilion	71.8°F	+5.5°F	2 of 132	Much warmer than normal
74	Livingston	71.2°F	+5.4°F	1 of 132	Much warmer than normal
75	Rock Island	70.7°F	+5.4°F	2 of 132	Much warmer than normal
76	Warren	70.9°F	+5.4°F	4 of 132	Much warmer than normal
77	Knox	70.7°F	+5.3°F	3 of 132	Much warmer than normal
78	Marshall	71.0°F	+5.3°F	1 of 132	Much warmer than normal
79	Peoria	71.4°F	+5.3°F	2 of 132	Much warmer than normal
80	Henry	70.1°F	+5.1°F	3 of 132	Much warmer than normal
81	Iroquois	70.8°F	+5.0°F	1 of 132	Much warmer than normal
82	Bureau	69.6°F	+4.9°F	4 of 132	Much warmer than normal
83	Kankakee	70.6°F	+4.9°F	1 of 132	Much warmer than normal
84	Putnam	70.3°F	+4.8°F	3 of 132	Much warmer than normal
85	Grundy	70.2°F	+4.4°F	1 of 132	Much warmer than normal
86	Jo Daviess	67.6°F	+4.4°F	5 of 132	Much warmer than normal
87	Whiteside	69.1°F	+4.4°F	5 of 132	Much warmer than normal
88	Carroll	68.1°F	+4.3°F	6 of 132	Much warmer than normal
89	Kane	68.5°F	+4.3°F	3 of 132	Much warmer than normal
90	Will	69.8°F	+4.3°F	2 of 132	Much warmer than normal
91	DeKalb	68.2°F	+4.2°F	5 of 132	Much warmer than normal
92	Kendall	69.5°F	+4.2°F	3 of 132	Much warmer than normal
93	LaSalle	69.5°F	+4.2°F	6 of 132	Much warmer than normal
94	Lee	68.3°F	+4.1°F	9 of 132	Much warmer than normal
95	DuPage	68.8°F	+4.0°F	6 of 132	Much warmer than normal
96	Stephenson	67.0°F	+4.0°F	8 of 132	Much warmer than normal
97	McHenry	67.2°F	+3.9°F	8 of 132	Much warmer than normal
98	Boone	67.1°F	+3.8°F	10 of 132	Much warmer than normal
99	Cook	69.0°F	+3.8°F	7 of 132	Much warmer than normal
100	Lake	67.7°F	+3.8°F	8 of 132	Much warmer than normal
101	Ogle	67.6°F	+3.8°F	9 of 132	Much warmer than normal
102	Winnebago	67.3°F	+3.8°F	8 of 132	Much warmer than normal

Get this data

This page's numbers, as JSON:

curl https://visualizedata.org/data/topics/climate/us-il.json

The climatedata.dev API it comes from (live, no key; every month since 1895 with its normal, anomaly and rank):

curl "https://api.climatedata.dev/v1/us-climate/tavg/us-il.json"

Open the JSON

What this can't tell you

A statewide average is not the average of its counties: NOAA computes it from its own grid, weighted by area.
The most recent months are preliminary and NOAA revises them in the next release.

How the answer is decided

Each month is ranked against the same month in every year on record (since 1895 for most places). The top tenth of the record is 'much warmer than normal', the top third 'warmer', the middle third 'near normal'. Counties are coloured by the same five words.

Sources

climatedata.dev us-climate, version 2026-10-25.6c7474e6d8 (U.S. public domain)
NOAA Monthly U.S. Climate Divisional Database (nClimDiv), statewide and national files (U.S. public domain)
climatedata.dev county-climate, version 2026-10-25.b4bbb5298a (U.S. public domain)
U.S. Census Bureau TIGERweb, counties (generalised) (U.S. public domain)
Built 2026-10-26. Download every county's answer (JSON)

Every topic for one county: How's Hennepin County?