Counties in Illinois by average annual temperature

Pulaski County had the highest average annual temperature of 102 counties in 2020, at 58.5 °F. Jo Daviess County had the lowest, at 49.1 °F. The median was 53.3 °F and the figure for Illinois was 53.3 °F. Source: NOAA National Centers for Environmental Information.

Highest58.5Pulaski County

Lowest49.1Jo Daviess County

Median53.3102 counties

Illinois53.3History

Top 40 counties, 2020

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

Full ranking

Rank	Counties	2020 °F	Change on 2019
1	Pulaski County	58.5	+0.5%
2	Alexander County	58.4	+0.3%
3	Massac County	58.3	+0.3%
4	Union County	57.4	+0.5%
5	Hardin County	57.3	+0.2%
5	Johnson County	57.3	+0.5%
5	Pope County	57.3	+0.4%
8	Gallatin County	57.2	+1.1%
9	Monroe County	57	+0.5%
9	White County	57	+1.1%
11	Hamilton County	56.9	+1.1%
12	Edwards County	56.8	+1.1%
12	Jackson County	56.8	+0.7%
12	Saline County	56.8	+0.5%
12	Wayne County	56.8	+1.1%
16	Williamson County	56.7	+0.5%
17	Franklin County	56.6	+0.5%
17	Wabash County	56.6	+0.9%
19	Jefferson County	56.5	+1.3%
19	St. Clair County	56.5	+0.7%
21	Perry County	56.4	+0.7%
21	Randolph County	56.4	+0.2%
23	Washington County	56.3	+1.3%
24	Clinton County	56.2	+1.3%
25	Lawrence County	55.9	+0.7%
26	Marion County	55.8	+1.6%
26	Richland County	55.8	+0.9%
28	Clay County	55.7	+1.3%
28	Madison County	55.7	+1.3%
30	Bond County	55.3	+1.5%
30	Crawford County	55.3	+1.1%
30	Jersey County	55.3	+1.7%
33	Calhoun County	55	+1.5%
33	Jasper County	55	+1.1%
35	Fayette County	54.7	+1.5%
36	Effingham County	54.5	+1.3%
36	Greene County	54.5	+1.5%
38	Clark County	54.3	+1.1%
38	Macoupin County	54.3	+1.7%
40	Cumberland County	54.2	+1.1%
40	Montgomery County	54.2	+1.9%
42	Pike County	53.8	+1.1%
42	Shelby County	53.8	+1.7%
44	Christian County	53.7	+1.9%
44	Scott County	53.7	+1.3%
46	Coles County	53.6	+1.3%
47	Adams County	53.4	+1.7%
47	Douglas County	53.4	+1.7%
47	Morgan County	53.4	+1.9%
47	Moultrie County	53.4	+1.5%
47	Sangamon County	53.4	+2.1%
52	Logan County	53.3	+2.3%
52	Macon County	53.3	+1.9%
52	Mason County	53.3	+2.3%
55	Cass County	53.2	+2.1%
56	Brown County	53.1	+1.5%
56	Edgar County	53.1	+1.5%
56	Menard County	53.1	+2.1%
56	Tazewell County	53.1	+2.7%
60	Schuyler County	53	+2.1%
61	Piatt County	52.9	+1.7%
62	De Witt County	52.8	+2.1%
62	Hancock County	52.8	+2.3%
64	Fulton County	52.6	+2.5%
65	Champaign County	52.5	+1.7%
66	Peoria County	52.4	+2.7%
66	Vermilion County	52.4	+1.9%
66	Woodford County	52.4	+3.1%
69	McLean County	52.3	+2.8%
70	McDonough County	52.2	+2.4%
71	Iroquois County	52.1	+2.4%
72	Kankakee County	52	+3.6%
72	Livingston County	52	+4%
72	Marshall County	52	+3.6%
75	Ford County	51.9	+2.4%
75	Grundy County	51.9	+3.8%
75	Henderson County	51.9	+2.8%
78	Putnam County	51.7	+4%
79	Cook County	51.6	+4.5%
80	LaSalle County	51.5	+4.5%
80	Will County	51.5	+3.6%
82	Mercer County	51.4	+3.8%
83	Rock Island County	51.3	+4.3%
84	Knox County	51.2	+3%
84	Stark County	51.2	+3.4%
84	Warren County	51.2	+2.8%
87	Kendall County	51.1	+3.9%
88	DuPage County	51	+4.3%
89	Henry County	50.9	+3.7%
89	Whiteside County	50.9	+4.5%
91	Bureau County	50.8	+3.9%
92	Lake County	50.5	+5.6%
93	Kane County	50.3	+4.6%
93	Lee County	50.3	+3.9%
95	Carroll County	50.2	+4.6%
95	Ogle County	50.2	+4.4%
97	DeKalb County	49.9	+4.4%
97	McHenry County	49.9	+5.3%
97	Winnebago County	49.9	+4.8%
100	Boone County	49.7	+5.1%
101	Stephenson County	49.2	+4.5%
102	Jo Daviess County	49.1	+4.9%

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, 2020) [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, 2020. 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=2020. 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, 2020. 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=2020.

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, 2020 [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=2020 (Accessed: 12 October 2026).

BibTeX

@misc{noaa_counties_in_illinois_by_2020,
  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, 2020}},
  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=2020. 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, 2020
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=2020
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2020.
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 58.5 °F in 2020, according to NOAA National Centers for Environmental Information.

Which county has the lowest average annual temperature?

Jo Daviess County, with 49.1 °F in 2020.

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.