Counties in Illinois by average annual temperature

Pulaski County had the highest average annual temperature of 102 counties in 2021, at 58.8 °F. Stephenson County had the lowest, at 49.4 °F. The median was 54 °F and the figure for Illinois was 53.8 °F. Source: NOAA National Centers for Environmental Information.

Highest58.8Pulaski County

Lowest49.4Stephenson County

Median54102 counties

Illinois53.8History

Map of counties, 2021

Under 52
52 to 53
53 to 54
54 to 55
55 to 57
57 and over

°F, 2021. Source: NOAA NCEI, NOAA Climate at a Glance, January to December average temperature, counties. Boundaries: U.S. Census Bureau cartographic boundary files.

Top 40 counties, 2021

°F. Source: NOAA NCEI, NOAA Climate at a Glance, January to December average temperature, counties. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2021 °F	Change on 2020
1	Pulaski County	58.8	+0.5%
2	Alexander County	58.7	+0.5%
3	Massac County	58.5	+0.3%
4	Union County	57.7	+0.5%
5	Monroe County	57.5	+0.9%
6	Hardin County	57.4	+0.2%
6	Johnson County	57.4	+0.2%
6	Pope County	57.4	+0.2%
9	Jackson County	57.1	+0.5%
10	Franklin County	57	+0.7%
10	Gallatin County	57	-0.3%
10	Hamilton County	57	+0.2%
10	Wayne County	57	+0.4%
14	Jefferson County	56.9	+0.7%
14	Williamson County	56.9	+0.4%
16	Edwards County	56.8	0%
16	Perry County	56.8	+0.7%
16	Randolph County	56.8	+0.7%
16	Saline County	56.8	0%
16	St. Clair County	56.8	+0.5%
16	White County	56.8	-0.4%
22	Wabash County	56.6	0%
22	Washington County	56.6	+0.5%
24	Clinton County	56.5	+0.5%
25	Madison County	56.2	+0.9%
26	Jersey County	56.1	+1.4%
26	Marion County	56.1	+0.5%
26	Richland County	56.1	+0.5%
29	Clay County	56	+0.5%
30	Lawrence County	55.9	0%
31	Bond County	55.8	+0.9%
32	Calhoun County	55.7	+1.3%
33	Jasper County	55.4	+0.7%
34	Crawford County	55.3	0%
35	Fayette County	55.2	+0.9%
35	Greene County	55.2	+1.3%
37	Effingham County	55	+0.9%
37	Macoupin County	55	+1.3%
39	Clark County	54.9	+1.1%
40	Cumberland County	54.8	+1.1%
41	Montgomery County	54.7	+0.9%
42	Coles County	54.4	+1.5%
42	Pike County	54.4	+1.1%
42	Scott County	54.4	+1.3%
45	Douglas County	54.2	+1.5%
46	Christian County	54.1	+0.7%
46	Shelby County	54.1	+0.6%
48	Adams County	54	+1.1%
48	Edgar County	54	+1.7%
48	Mason County	54	+1.3%
48	Morgan County	54	+1.1%
48	Moultrie County	54	+1.1%
53	Logan County	53.9	+1.1%
53	Sangamon County	53.9	+0.9%
55	Macon County	53.8	+0.9%
56	Cass County	53.7	+0.9%
56	Menard County	53.7	+1.1%
56	Tazewell County	53.7	+1.1%
59	Piatt County	53.6	+1.3%
60	Brown County	53.5	+0.8%
61	De Witt County	53.4	+1.1%
62	Fulton County	53.3	+1.3%
62	Schuyler County	53.3	+0.6%
64	Champaign County	53.2	+1.3%
64	Hancock County	53.2	+0.8%
64	Peoria County	53.2	+1.5%
67	McLean County	53.1	+1.5%
68	Livingston County	52.9	+1.7%
68	Woodford County	52.9	+1%
70	Vermilion County	52.8	+0.8%
71	McDonough County	52.7	+1%
72	Ford County	52.5	+1.2%
72	Henderson County	52.5	+1.2%
72	Marshall County	52.5	+1%
75	Cook County	52.2	+1.2%
75	Grundy County	52.2	+0.6%
75	Iroquois County	52.2	+0.2%
78	Putnam County	52.1	+0.8%
79	Kankakee County	52	0%
80	Mercer County	51.9	+1%
80	Rock Island County	51.9	+1.2%
80	Will County	51.9	+0.8%
83	DuPage County	51.7	+1.4%
83	Knox County	51.7	+1%
83	Stark County	51.7	+1%
83	Warren County	51.7	+1%
87	LaSalle County	51.6	+0.2%
88	Kendall County	51.5	+0.8%
89	Bureau County	51.4	+1.2%
89	Henry County	51.4	+1%
91	Whiteside County	51.2	+0.6%
92	Lake County	51	+1%
93	Kane County	50.8	+1%
94	Lee County	50.7	+0.8%
95	Ogle County	50.6	+0.8%
95	Winnebago County	50.6	+1.4%
97	Boone County	50.5	+1.6%
97	DeKalb County	50.5	+1.2%
99	McHenry County	50.3	+0.8%
100	Carroll County	50.1	-0.2%
101	Jo Daviess County	49.4	+0.6%
101	Stephenson County	49.4	+0.4%

Other periods

About this ranking

Mean air temperature from January to December, in degrees Fahrenheit: the average of the 12 monthly mean temperatures. NOAA computes it from its climate divisional dataset (nClimDiv): station readings interpolated onto a 5 km grid and averaged over the area.

Values are area averages, so a county with mountains and valleys has one value for very different local climates. NOAA revises the last two years every month.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. Equal values share a rank.

How to cite

NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December average temperature, counties. 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/county/mapping. 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 average temperature, counties (Counties in Illinois by average annual temperature, 2021) [Data set]. Retrieved October 12, 2026, from https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/mapping

MLA 9

NOAA Climate at a Glance, January to December average temperature, counties, Counties in Illinois by average annual temperature, 2021. NOAA National Centers for Environmental Information, 6 Oct. 2026, https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/mapping. Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2021. Accessed 12 Oct. 2026.

Chicago (author-date)

NOAA National Centers for Environmental Information. 2026. NOAA Climate at a Glance, January to December average temperature, counties. Counties in Illinois by average annual temperature, 2021. Dataset. Accessed October 12, 2026. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/mapping. Also distributed by Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2021.

Harvard

NOAA National Centers for Environmental Information (2026) NOAA Climate at a Glance, January to December average temperature, counties, Counties in Illinois by average annual temperature, 2021 [Dataset]. Available at: https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/mapping, via Invokely: https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2021 (Accessed: 12 October 2026).

BibTeX

@misc{noaa_counties_in_illinois_by_2021,
  author = {{NOAA National Centers for Environmental Information}},
  title = {{NOAA Climate at a Glance, January to December average temperature, counties: Counties in Illinois by average annual temperature, 2021}},
  year = {2026},
  howpublished = {Data set},
  url = {https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/county/mapping},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2021. Publisher attribution: NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December average temperature, counties. 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/county/mapping. Retrieved 2026-10-12.},
}

RIS

TY  - DATA
AU  - NOAA National Centers for Environmental Information
TI  - NOAA Climate at a Glance, January to December average temperature, counties: Counties in Illinois by average annual temperature, 2021
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/county/mapping
L2  - https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2021
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2021.
N1  - Publisher attribution: NOAA National Centers for Environmental Information, Climate at a Glance. NOAA Climate at a Glance, January to December average temperature, counties. 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/county/mapping. Retrieved 2026-10-12.
ER  -

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Questions

Which county has the highest average annual temperature?

Pulaski County, with 58.8 °F in 2021, according to NOAA National Centers for Environmental Information.

Which county has the lowest average annual temperature?

Stephenson County, with 49.4 °F in 2021.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: NOAA National Centers for Environmental Information, NOAA Climate at a Glance, January to December average temperature, counties. Retrieved 2026-10-12.