Counties in Illinois by average annual temperature

Alexander County had the highest average annual temperature of 102 counties in 2019, at 58.2 °F. Jo Daviess County had the lowest, at 46.8 °F. The median was 52.3 °F and the figure for Illinois was 52.1 °F. Source: NOAA National Centers for Environmental Information.

Highest58.2Alexander County

Lowest46.8Jo Daviess County

Median52.3102 counties

Illinois52.1History

Map of counties, 2019

Under 49
49 to 51
51 to 52
52 to 54
54 to 56
56 and over

°F, 2019. 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, 2019

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

Full ranking

Rank	Counties	2019 °F	Change on 2018
1	Alexander County	58.2	+0.3%
1	Pulaski County	58.2	+0.3%
3	Massac County	58.1	+0.3%
4	Hardin County	57.2	+0.5%
5	Pope County	57.1	+0.4%
5	Union County	57.1	+0.4%
7	Johnson County	57	+0.4%
8	Monroe County	56.7	-0.4%
9	Gallatin County	56.6	0%
10	Saline County	56.5	+0.4%
11	Jackson County	56.4	+0.4%
11	White County	56.4	+0.2%
11	Williamson County	56.4	+0.4%
14	Franklin County	56.3	+0.4%
14	Hamilton County	56.3	+0.4%
14	Randolph County	56.3	0%
17	Edwards County	56.2	0%
17	Wayne County	56.2	+0.5%
19	St. Clair County	56.1	-0.7%
19	Wabash County	56.1	-0.2%
21	Perry County	56	+0.4%
22	Jefferson County	55.8	+0.5%
23	Washington County	55.6	+0.2%
24	Clinton County	55.5	-0.4%
24	Lawrence County	55.5	-0.4%
26	Richland County	55.3	-0.2%
27	Clay County	55	0%
27	Madison County	55	-0.9%
29	Marion County	54.9	0%
30	Crawford County	54.7	-0.4%
31	Bond County	54.5	-0.5%
32	Jasper County	54.4	-0.4%
32	Jersey County	54.4	-0.9%
34	Calhoun County	54.2	-0.9%
35	Fayette County	53.9	-0.6%
36	Effingham County	53.8	-0.4%
37	Clark County	53.7	-0.4%
37	Greene County	53.7	-1.1%
39	Cumberland County	53.6	-0.6%
40	Macoupin County	53.4	-0.9%
41	Montgomery County	53.2	-0.7%
41	Pike County	53.2	-1.7%
43	Scott County	53	-1.7%
44	Coles County	52.9	-0.8%
44	Shelby County	52.9	-0.8%
46	Christian County	52.7	-1.1%
47	Moultrie County	52.6	-0.6%
48	Adams County	52.5	-1.1%
48	Douglas County	52.5	-0.8%
50	Morgan County	52.4	-1.3%
51	Brown County	52.3	-1.9%
51	Edgar County	52.3	-0.6%
51	Macon County	52.3	-0.6%
51	Sangamon County	52.3	-1.5%
55	Cass County	52.1	-1.3%
55	Logan County	52.1	-0.8%
55	Mason County	52.1	-1.1%
58	Menard County	52	-1.3%
58	Piatt County	52	-0.6%
60	Schuyler County	51.9	-1.5%
61	De Witt County	51.7	-0.6%
61	Tazewell County	51.7	-1.1%
63	Champaign County	51.6	-1%
63	Hancock County	51.6	-1%
65	Vermilion County	51.4	-1%
66	Fulton County	51.3	-1.2%
67	McDonough County	51	-1.2%
67	Peoria County	51	-1.2%
69	Iroquois County	50.9	-0.6%
69	McLean County	50.9	-0.6%
71	Woodford County	50.8	-1%
72	Ford County	50.7	-1%
73	Henderson County	50.5	-0.8%
74	Kankakee County	50.2	-1%
74	Marshall County	50.2	-0.8%
76	Grundy County	50	-0.8%
76	Livingston County	50	-0.4%
78	Warren County	49.8	-0.8%
79	Knox County	49.7	-0.8%
79	Putnam County	49.7	-0.8%
79	Will County	49.7	-0.8%
82	Mercer County	49.5	-1%
82	Stark County	49.5	-0.8%
84	Cook County	49.4	-1.2%
85	LaSalle County	49.3	-1%
86	Kendall County	49.2	-0.8%
86	Rock Island County	49.2	-1.4%
88	Henry County	49.1	-1%
89	Bureau County	48.9	-0.8%
89	DuPage County	48.9	-1.4%
91	Whiteside County	48.7	-1%
92	Lee County	48.4	-0.8%
93	Kane County	48.1	-1%
93	Ogle County	48.1	-0.6%
95	Carroll County	48	-0.8%
96	DeKalb County	47.8	-1%
96	Lake County	47.8	-1.4%
98	Winnebago County	47.6	-0.2%
99	McHenry County	47.4	-0.6%
100	Boone County	47.3	-0.2%
101	Stephenson County	47.1	-1.3%
102	Jo Daviess County	46.8	-1.7%

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, 2019) [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, 2019. 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=2019. 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, 2019. 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=2019.

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, 2019 [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=2019 (Accessed: 12 October 2026).

BibTeX

@misc{noaa_counties_in_illinois_by_2019,
  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, 2019}},
  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=2019. 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, 2019
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=2019
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/average-annual-temperature/illinois-counties?period=2019.
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  -

Embed this chart

Paste this code into a web page or a blog post. The chart shows the latest figures as they are published, with the source and a link back to this page.

Embed code

<iframe src="https://invokely.ai/embed/rankings/average-annual-temperature/illinois-counties?period=2019" width="760" height="500" title="Counties in Illinois by average annual temperature, 2019, chart from Invokely" loading="lazy" style="border:0;width:100%;max-width:760px" referrerpolicy="strict-origin-when-cross-origin"></iframe>

Sites that read oEmbed links, such as WordPress, can show the chart when you paste the link to this page.

Use this data in your AI agent

Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:

Rank Counties in Illinois by average annual temperature using official data, and cite the source.

rank_places {"indicator":"average_temperature_annual","level":"province","within":"Illinois","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=average_temperature_annual&level=province&within=Illinois&limit=10

Connect Claude, ChatGPT or Cursor in one step. The trial answers 25 calls a day without an account.

Questions

Which county has the highest average annual temperature?

Alexander County, with 58.2 °F in 2019, according to NOAA National Centers for Environmental Information.

Which county has the lowest average annual temperature?

Jo Daviess County, with 46.8 °F in 2019.

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.