Counties in Illinois by average annual temperature

Massac County had the highest average annual temperature of 102 counties in 2017, at 59.5 °F. Jo Daviess County had the lowest, at 49.5 °F. The median was 55 °F and the figure for Illinois was 54.4 °F. Source: NOAA National Centers for Environmental Information.

Highest59.5Massac County

Lowest49.5Jo Daviess County

Median55102 counties

Illinois54.4History

Map of counties, 2017

Under 52
52 to 53
53 to 55
55 to 56
56 to 58
58 and over

°F, 2017. 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, 2017

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

Full ranking

Rank	Counties	2017 °F	Change on 2016
1	Massac County	59.5	-0.2%
2	Pulaski County	59.3	-0.2%
3	Alexander County	59.2	-0.3%
4	Monroe County	59	0%
5	Hardin County	58.7	+0.2%
5	Pope County	58.7	+0.2%
5	St. Clair County	58.7	+0.2%
8	Gallatin County	58.5	-0.2%
8	White County	58.5	-0.3%
10	Hamilton County	58.4	+0.2%
10	Johnson County	58.4	0%
12	Randolph County	58.3	-0.2%
12	Saline County	58.3	+0.3%
12	Union County	58.3	-0.2%
15	Wayne County	58.2	+0.2%
16	Edwards County	58.1	0%
17	Franklin County	57.8	-0.2%
17	Jackson County	57.8	-0.5%
17	Williamson County	57.8	-0.2%
20	Clinton County	57.6	0%
20	Perry County	57.6	-0.3%
20	Wabash County	57.6	0%
23	Madison County	57.5	-0.3%
23	Washington County	57.5	0%
25	Jefferson County	57.4	+0.2%
26	Richland County	56.9	+0.4%
27	Bond County	56.8	0%
27	Clay County	56.8	+0.2%
27	Lawrence County	56.8	+0.4%
27	Marion County	56.8	+0.2%
31	Jersey County	56.6	-0.9%
32	Calhoun County	56.4	-1.1%
33	Crawford County	56.2	+0.2%
33	Fayette County	56.2	-0.4%
35	Greene County	56	-0.7%
35	Jasper County	56	+0.2%
37	Effingham County	55.9	+0.2%
37	Pike County	55.9	-0.5%
39	Macoupin County	55.8	-0.5%
40	Cumberland County	55.7	+0.4%
40	Montgomery County	55.7	0%
40	Scott County	55.7	-0.5%
43	Clark County	55.6	0%
44	Shelby County	55.4	+0.2%
45	Christian County	55.3	0%
45	Coles County	55.3	+0.4%
45	Sangamon County	55.3	-0.5%
48	Morgan County	55.2	-0.9%
49	Adams County	55	-0.5%
49	Brown County	55	-0.2%
49	Cass County	55	-0.4%
49	Douglas County	55	+0.2%
49	Menard County	55	-0.5%
54	Moultrie County	54.9	+0.2%
55	Mason County	54.8	-0.2%
56	Edgar County	54.7	-0.2%
57	Macon County	54.6	-0.2%
58	Logan County	54.5	-0.7%
58	Schuyler County	54.5	+0.2%
60	Piatt County	54.4	0%
61	Champaign County	54.2	0%
61	Tazewell County	54.2	-1.1%
63	Hancock County	54.1	-0.9%
64	De Witt County	54	-0.6%
65	Fulton County	53.8	-0.4%
65	Vermilion County	53.8	-0.4%
67	Peoria County	53.6	-0.7%
68	McDonough County	53.5	-0.9%
69	McLean County	53.4	-1.3%
70	Woodford County	53.3	-1.3%
71	Ford County	53.2	-0.6%
72	Henderson County	53.1	-1.1%
73	Iroquois County	52.9	-0.8%
74	Livingston County	52.6	-1.7%
75	Marshall County	52.5	-1.1%
76	Kankakee County	52.4	-0.8%
77	Warren County	52.2	-1.5%
78	Grundy County	52.1	-1.5%
78	Knox County	52.1	-1.3%
78	Mercer County	52.1	-1.7%
81	Stark County	52	-1%
82	Rock Island County	51.9	-1.7%
82	Will County	51.9	-1%
84	Putnam County	51.8	-1.5%
85	Cook County	51.7	-1%
85	Henry County	51.7	-1.7%
87	LaSalle County	51.5	-1.7%
88	Whiteside County	51.4	-1.7%
89	Kendall County	51.3	-1.5%
90	DuPage County	51.1	-1.2%
91	Bureau County	51	-1.5%
92	Lee County	50.8	-1.7%
93	Carroll County	50.5	-1.8%
94	Ogle County	50.4	-1.6%
95	Kane County	50.3	-1.4%
96	DeKalb County	50.1	-1.8%
96	Lake County	50.1	-1.2%
96	Winnebago County	50.1	-0.8%
99	Stephenson County	49.7	-1.8%
100	Boone County	49.6	-1.4%
100	McHenry County	49.6	-1.6%
102	Jo Daviess County	49.5	-1.8%

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, 2017) [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, 2017. 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=2017. 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, 2017. 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=2017.

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, 2017 [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=2017 (Accessed: 12 October 2026).

BibTeX

@misc{noaa_counties_in_illinois_by_2017,
  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, 2017}},
  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=2017. 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, 2017
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=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2017.
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?

Massac County, with 59.5 °F in 2017, according to NOAA National Centers for Environmental Information.

Which county has the lowest average annual temperature?

Jo Daviess County, with 49.5 °F in 2017.

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.