Data report · 2026

Iowa Water Damage Risk Index

Where in Iowa is a house most likely to take on water? We combined Census housing age with ten years of daily weather for 99 of Iowa's 99 counties to rank them.

Highest index

Worth

Score 78 of 100

Most pipe-freeze nights

Dickinson

81 nights ≤ 20°F a year

Oldest housing

Audubon

64% built before 1960

Most heavy-rain days

Allamakee

9.3 days ≥ 1 inch a year

< 3939–4747–5252–62≥ 62 index (0–100)

Key findings

The five highest-scoring counties are Worth, Fayette, Audubon, Floyd, Mitchell. Each combines old housing with harsher-than-average winters or frequent downpours.
Audubon County has the oldest housing in the state, with 64% of homes built before 1960, against a county median of 48%.
Dickinson County averaged 81 nights a year at 20°F or colder, the most of any county in the data. The county median is 62.
Dallas County has the newest housing, with 65% 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	Worth	78	77	61%	8.2	16
2	Fayette	75	71	56%	9.1	18
3	Audubon	73	65	64%	8.2	24
4	Floyd	72	72	53%	8.7	20
5	Mitchell	70	74	52%	8.4	16
6	Greene	68	63	57%	7.5	31
7	Adams	67	58	56%	7.9	33
8	Howard	67	77	50%	8.6	11
9	Harrison	66	60	53%	7.4	38
10	Osceola	66	81	59%	6.5	20
11	Shelby	66	63	59%	7.3	29
12	Taylor	66	52	57%	8.5	39
13	Butler	65	68	52%	8	22
14	Franklin	65	69	60%	7	21
15	Winneshiek	65	70	49%	9.2	17
16	Clayton	64	66	50%	8.9	22
17	O'Brien	63	78	52%	6.9	22
18	Cerro Gordo	62	73	52%	7.2	18
19	Cherokee	62	74	52%	6.8	26
20	Emmet	62	81	58%	6	18
21	Pocahontas	62	74	62%	6	22
22	Page	61	51	56%	7.7	42
23	Chickasaw	60	72	45%	8.6	16
24	Cass	59	58	55%	7.2	30
25	Clinton	59	51	53%	8.5	36
26	Ida	59	68	60%	5.9	28
27	Adair	58	60	52%	7.4	30
28	Hamilton	58	66	58%	6.7	22
29	Hancock	58	76	50%	7.2	16
30	Montgomery	57	54	51%	8	37
31	Palo Alto	57	76	53%	6.2	21
32	Bremer	55	69	40%	8.8	21
33	Des Moines	55	45	51%	8.2	44
34	Hardin	55	65	56%	6.5	24
35	Winnebago	55	78	48%	7	16
36	Fremont	54	50	52%	7.5	46
37	Allamakee	53	67	39%	9.3	22
38	Lee	53	43	50%	8.1	50
39	Sac	53	68	54%	5.3	29
40	Delaware	52	65	44%	8	22
41	Marshall	52	60	53%	6.5	30
42	Union	52	56	48%	7.4	34
43	Webster	52	68	55%	5.7	24
44	Boone	51	60	50%	6.9	32
45	Monona	51	64	54%	5.7	32
46	Calhoun	50	69	52%	5.8	28
47	Grundy	50	64	48%	7.1	25
48	Kossuth	50	77	48%	6.3	20
49	Wright	50	72	50%	6.5	17
50	Black Hawk	49	66	41%	7.7	25
51	Crawford	49	66	42%	7.3	28
52	Woodbury	49	67	51%	5.9	30
53	Dickinson	48	81	27%	7.3	20
54	Keokuk	48	55	57%	5.9	34
55	Tama	48	63	53%	6.1	26
56	Carroll	47	66	45%	6.8	27
57	Clay	47	76	43%	6.5	22
58	Jackson	47	54	40%	9	31
59	Lyon	47	80	43%	6.4	21
60	Ringgold	47	52	42%	8.4	39
61	Wayne	47	54	44%	7.6	36
62	Appanoose	46	54	47%	7.2	37
63	Guthrie	46	61	45%	7	29
64	Humboldt	45	72	49%	5.7	21
65	Sioux	45	78	33%	6.8	23
66	Cedar	44	57	47%	7	30
67	Dubuque	44	58	37%	8.5	25
68	Jones	44	56	42%	7.8	27
69	Benton	43	66	46%	6.5	24
70	Buena Vista	43	72	45%	5.2	27
71	Poweshiek	43	58	40%	7.4	31
72	Buchanan	42	69	36%	7.2	21
73	Decatur	42	51	40%	7.8	42
74	Story	42	59	23%	7.8	32
75	Louisa	41	49	44%	7.3	40
76	Muscatine	41	54	40%	7.7	35
77	Pottawattamie	41	56	43%	6.9	38
78	Lucas	40	53	48%	6.6	38
79	Clarke	39	53	30%	7.7	40
80	Iowa	39	58	43%	6.6	32
81	Plymouth	39	71	39%	6.3	26
82	Jasper	38	56	43%	6.6	36
83	Scott	38	48	32%	8.2	40
84	Mills	37	53	38%	7.1	43
85	Wapello	37	50	52%	4.9	40
86	Van Buren	36	49	42%	7.1	42
87	Henry	35	50	41%	7.2	38
88	Mahaska	35	54	47%	5.6	38
89	Polk	35	54	28%	7	42
90	Jefferson	34	51	44%	6.7	37
91	Davis	33	49	39%	7.2	41
92	Washington	33	53	46%	6	36
93	Linn	32	62	27%	6.8	28
94	Warren	32	53	19%	7	42
95	Johnson	30	58	17%	6.7	32
96	Madison	30	56	34%	6.5	36
97	Monroe	29	52	41%	6.2	39
98	Marion	26	54	30%	6.1	39
99	Dallas	24	56	13%	6.1	36

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