Data report · 2026

Illinois Water Damage Risk Index

Where in Illinois is a house most likely to take on water? We combined Census housing age with ten years of daily weather for 102 of Illinois's 102 counties to rank them.

Highest index

Stephenson

Score 72 of 100

Most pipe-freeze nights

Jo Daviess

57 nights ≤ 20°F a year

Oldest housing

Ford

58% built before 1960

Most heavy-rain days

Massac

13.8 days ≥ 1 inch a year

< 4242–4848–5252–60≥ 60 index (0–100)

Key findings

The five highest-scoring counties are Stephenson, Carroll, Brown, Knox, Whiteside. Each combines old housing with harsher-than-average winters or frequent downpours.
Ford County has the oldest housing in the state, with 58% of homes built before 1960, against a county median of 38%.
Jo Daviess County averaged 57 nights a year at 20°F or colder, the most of any county in the data. The county median is 35.
Kendall County has the newest housing, with 55% of homes built since 2000, which pulls its index down even where winters are cold.

Weather: NOAA nClimGrid-Daily county averages, 2015–2024. Housing: ACS 2020-2024.

All counties

Select a column header to sort.

Rank	County	Index	Freeze nights	Pre-1960 homes	Heavy-rain days	Muggy nights
1	Stephenson	72	56	51%	9	24
2	Carroll	71	52	53%	8.4	29
3	Brown	66	37	50%	8.8	52
4	Knox	66	45	54%	7.7	39
5	Whiteside	66	48	48%	8.6	35
6	Fulton	65	40	50%	8.4	48
7	Henry	65	47	49%	8	37
8	Lawrence	64	24	46%	12.6	69
9	Lee	64	48	50%	8	28
10	Ford	63	40	58%	7.9	36
11	Greene	63	31	52%	8.7	61
12	Bureau	62	48	53%	7	30
13	McDonough	62	41	43%	9.6	47
14	Pike	62	33	49%	8.8	59
15	Warren	62	46	56%	6.8	40
16	Hancock	61	39	46%	8.1	56
17	Mercer	61	48	48%	7.2	40
18	Rock Island	61	47	46%	7.7	41
19	Franklin	60	21	47%	11.5	74
20	Stark	60	47	54%	6.8	34
21	White	60	20	47%	10.9	77
22	Mason	59	37	51%	7.3	51
23	Wabash	59	22	44%	12.5	73
24	Adams	58	36	44%	8.7	58
25	Crawford	58	26	45%	10.5	66
26	Edwards	57	21	42%	11.9	75
27	Scott	57	35	46%	8.4	53
28	Shelby	57	31	44%	9.9	53
29	Christian	56	33	47%	8.4	50
30	Marshall	56	44	49%	6.8	40
31	Montgomery	56	31	46%	8.9	52
32	Clay	55	24	38%	12.6	68
33	Jo Daviess	55	57	35%	8.8	26
34	Morgan	55	36	42%	9	48
35	Schuyler	55	38	38%	9.1	51
36	Livingston	54	42	49%	6.9	38
37	Macoupin	54	31	45%	8.4	59
38	Fayette	53	28	38%	10.5	58
39	Washington	53	24	37%	11.5	69
40	Calhoun	52	30	42%	8.7	67
41	De Witt	52	37	52%	6.3	45
42	Saline	52	20	38%	11.4	76
43	Cook	51	40	49%	6.3	41
44	Cumberland	51	28	38%	10.2	57
45	Hamilton	51	20	44%	10.2	74
46	Iroquois	51	40	50%	6.5	36
47	LaSalle	51	46	47%	6.3	34
48	Alexander	50	16	36%	12.7	84
49	Edgar	50	32	46%	8	43
50	Gallatin	50	19	39%	10.7	79
51	Madison	50	26	36%	10	74
52	Peoria	50	40	42%	7.3	48
53	Vermilion	50	37	53%	6.2	39
54	Wayne	50	21	37%	11.7	72
55	Winnebago	50	52	36%	7.8	25
56	Clark	49	29	38%	9.3	53
57	Henderson	49	44	37%	7.5	46
58	Marion	49	25	33%	12	65
59	Ogle	49	50	35%	7.9	27
60	Pulaski	49	16	35%	13.3	86
61	Union	49	19	35%	12.9	79
62	Cass	48	38	42%	7.4	48
63	Perry	48	23	35%	11.4	72
64	Randolph	48	22	37%	10	75
65	Tazewell	48	38	38%	7.6	51
66	Hardin	47	18	33%	13.2	79
67	Jasper	47	25	34%	10.8	67
68	Logan	47	36	44%	7.1	50
69	Macon	47	34	45%	7	51
70	St. Clair	47	24	32%	10.6	79
71	Coles	46	30	40%	8.3	51
72	Massac	46	17	30%	13.8	85
73	Richland	46	23	33%	11.8	68
74	Woodford	46	41	36%	7.5	43
75	Bond	44	27	34%	9.6	62
76	Jersey	44	28	32%	9.3	71
77	Moultrie	44	32	42%	7.5	50
78	Pope	44	18	27%	13.7	79
79	Effingham	43	28	28%	10.3	60
80	Jefferson	43	23	28%	11.2	69
81	Clinton	42	24	27%	10.7	69
82	Jackson	42	21	24%	11.8	75
83	Douglas	41	32	41%	7.1	49
84	Johnson	41	19	14%	13.7	79
85	Boone	40	52	26%	7.2	26
86	Williamson	40	20	27%	11.3	75
87	Kane	38	48	24%	7.2	30
88	McHenry	38	51	18%	7.6	25
89	Menard	38	36	32%	7.6	50
90	Putnam	38	46	35%	5.9	36
91	Sangamon	38	34	32%	7.8	51
92	DeKalb	37	50	25%	6.9	28
93	Monroe	37	22	21%	9.5	80
94	Kankakee	32	41	32%	6.1	36
95	McLean	32	40	23%	7	41
96	Lake	31	44	21%	6.9	30
97	Will	31	42	15%	7	37
98	DuPage	30	45	18%	6.6	37
99	Kendall	30	46	9%	6.7	36
100	Piatt	30	35	33%	6.3	47
101	Grundy	28	43	20%	6	38
102	Champaign	26	36	24%	6.6	42

Methodology

For each county with weather data, we convert four factors to a percentile rank among those counties (0 = lowest, 100 = highest), then take a weighted average:

Pipe-freeze nights (nights ≤ 20°F / yr), weight 30%
Homes built before 1960 (% of homes), weight 30%
Heavy-rain days (days ≥ 1 in / yr), weight 25%
Muggy nights (nights ≥ 65°F / yr), weight 15%

Freezing weather and old plumbing get the most weight because burst and failing supply lines are among the most common causes of household water damage. Heavy rain drives basement flooding and sewer backups, and warm, muggy nights mark the humid air that lets mold follow. The index is relative: a low score means lower risk than other Illinois counties, not no risk.

Limits: weather values are county-wide averages, so hollows, ridges and lakeshores can differ; ACS housing figures are survey estimates; the index doesn't account for floodplains, soil, or local sewer systems. Full details on our data sources page.

Cite this data

You're welcome to use these figures with attribution. Suggested citation:

Local Water & Mold, "Illinois Water Damage Risk Index 2026," https://localwatermold.com/illinois/illinois-water-damage-risk/. Data: U.S. Census Bureau ACS 2020-2024; NOAA nClimGrid-Daily 2015–2024.