Tornado Risk in Iowa

All Iowa counties ranked by FEMA National Risk Index tornado score

Tornado risk — violently rotating columns of air capable of catastrophic local damage — is rated for 99 of 99 Iowa counties in FEMA's National Risk Index. Johnson County carries the state's highest tornado score at 98.2, with $36M in expected annual tornado losses.

8 Iowa counties are rated High or Very High for tornado, and expected annual losses from tornado total roughly $354M statewide. The full ranking below links to each county's complete 18-hazard risk profile.

County Rankings — Tornado

#CountyTornado ScoreRatingAnn. Freq.Ann. Loss
1 Johnson County
98.2
High 0.59 / yr $36M
2 Polk County
98.1
High 0.59 / yr $31M
3 Woodbury County
96.5
High 0.71 / yr $16M
4 Linn County
95.5
High 0.68 / yr $16M
5 Pottawattamie County
95.2
High 0.82 / yr $14M
6 Webster County
92.1
High 0.69 / yr $10M
7 Black Hawk County
91.4
High 0.54 / yr $9M
8 Story County
91.3
High 0.59 / yr $10M
9 Cerro Gordo County
89.3
Medium 0.54 / yr $7M
10 Carroll County
85.5
Medium 0.51 / yr $6M
11 Dallas County
84.7
Medium 0.58 / yr $10M
12 Dubuque County
84.0
Medium 0.51 / yr $9M
13 Scott County
82.9
Medium 0.43 / yr $5M
14 Marshall County
82.7
Medium 0.60 / yr $4M
15 Crawford County
82.4
Medium 0.58 / yr $5M
16 Wapello County
81.8
Medium 0.31 / yr $4M
17 Sioux County
79.4
Medium 0.68 / yr $7M
18 Clinton County
79.0
Medium 0.66 / yr $4M
19 Plymouth County
77.4
Medium 0.74 / yr $4M
20 Cass County
75.8
Medium 0.48 / yr $3M
21 Buena Vista County
74.0
Medium 0.48 / yr $3M
22 Calhoun County
73.6
Medium 0.52 / yr $3M
23 Appanoose County
73.1
Medium 0.33 / yr $2M
24 Hardin County
72.2
Medium 0.58 / yr $3M
25 Fayette County
71.5
Medium 0.58 / yr $2M
26 Lee County
70.3
Medium 0.38 / yr $2M
27 Jasper County
70.3
Medium 0.73 / yr $3M
28 Page County
69.6
Medium 0.42 / yr $2M
29 Des Moines County
69.4
Medium 0.35 / yr $3M
30 Davis County
68.7
Medium 0.31 / yr $2M
31 Floyd County
68.0
Medium 0.45 / yr $2M
32 Marion County
67.7
Medium 0.48 / yr $3M
33 Warren County
65.9
Medium 0.50 / yr $4M
34 Greene County
65.5
Medium 0.55 / yr $3M
35 Hamilton County
64.8
Low 0.58 / yr $2M
36 Guthrie County
64.1
Low 0.57 / yr $3M
37 Dickinson County
64.0
Low 0.31 / yr $3M
38 Shelby County
63.2
Low 0.50 / yr $3M
39 Adair County
62.4
Low 0.52 / yr $2M
40 Montgomery County
61.6
Low 0.34 / yr $2M
41 Kossuth County
61.1
Low 0.81 / yr $3M
42 Winneshiek County
60.8
Low 0.46 / yr $2M
43 Cherokee County
60.8
Low 0.47 / yr $2M
44 Harrison County
60.1
Low 0.56 / yr $2M
45 Sac County
60.0
Low 0.48 / yr $3M
46 Iowa County
59.9
Low 0.55 / yr $2M
47 Poweshiek County
59.8
Low 0.57 / yr $2M
48 Audubon County
59.7
Low 0.39 / yr $2M
49 Chickasaw County
59.3
Low 0.42 / yr $2M
50 Ida County
59.1
Low 0.34 / yr $2M
51 Delaware County
58.5
Low 0.49 / yr $2M
52 Monona County
58.0
Low 0.55 / yr $2M
53 Tama County
57.4
Low 0.74 / yr $1M
54 Lucas County
57.3
Low 0.33 / yr $1M
55 Boone County
57.2
Low 0.58 / yr $3M
56 Union County
57.1
Low 0.34 / yr $1M
57 Washington County
57.0
Low 0.49 / yr $2M
58 Mills County
55.9
Low 0.38 / yr $2M
59 Allamakee County
55.7
Low 0.40 / yr $1M
60 Wayne County
55.2
Low 0.36 / yr $1M
61 Muscatine County
55.0
Low 0.42 / yr $2M
62 Madison County
54.9
Low 0.51 / yr $1M
63 Jackson County
54.8
Low 0.60 / yr $2M
64 Van Buren County
54.7
Low 0.32 / yr $1M
65 Mahaska County
54.6
Low 0.47 / yr $2M
66 Wright County
54.4
Low 0.55 / yr $1M
67 Taylor County
54.3
Low 0.40 / yr $1M
68 Jefferson County
54.1
Low 0.32 / yr $1M
69 Clayton County
54.0
Low 0.58 / yr $2M
70 Clay County
53.8
Low 0.44 / yr $2M
71 Bremer County
52.3
Low 0.39 / yr $2M
72 Jones County
51.0
Low 0.55 / yr $2M
73 Hancock County
50.5
Low 0.51 / yr $1M
74 Franklin County
50.3
Low 0.57 / yr $2M
75 Pocahontas County
49.7
Low 0.50 / yr $1M
76 O'Brien County
48.7
Low 0.48 / yr $2M
77 Henry County
48.5
Low 0.34 / yr $1M
78 Butler County
48.3
Low 0.57 / yr $2M
79 Decatur County
48.3
Low 0.38 / yr $1M
80 Mitchell County
47.7
Low 0.38 / yr $1M
81 Lyon County
45.9
Low 0.50 / yr $2M
82 Winnebago County
45.8
Low 0.34 / yr $1M
83 Fremont County
45.7
Low 0.44 / yr $1M
84 Cedar County
45.6
Low 0.55 / yr $2M
85 Humboldt County
45.5
Low 0.39 / yr $1M
86 Clarke County
44.6
Low 0.34 / yr $1M
87 Benton County
43.6
Low 0.67 / yr $2M
88 Emmet County
43.2
Low 0.32 / yr $1M
89 Osceola County
42.7
Low 0.32 / yr $877K
90 Keokuk County
42.3
Low 0.47 / yr $1M
91 Howard County
40.6
Low 0.34 / yr $1M
92 Monroe County
39.9
Low 0.31 / yr $1M
93 Palo Alto County
38.8
Low 0.46 / yr $1M
94 Adams County
38.0
Low 0.34 / yr $848K
95 Buchanan County
37.5
Low 0.51 / yr $1M
96 Worth County
36.0
Low 0.34 / yr $1M
97 Grundy County
34.8
Low 0.52 / yr $1M
98 Louisa County
34.2
Low 0.37 / yr $828K
99 Ringgold County
31.5
Low 0.39 / yr $775K

99 Iowa counties with measurable tornado risk. See the national tornado ranking or all Iowa counties by overall risk.

Frequently Asked Questions

Which Iowa county has the highest tornado risk?

Johnson County has the highest FEMA tornado risk score in Iowa at 98.2 (High), with $36M in expected annual losses and about 0.59 events per year.

How many Iowa counties face significant tornado risk?

99 Iowa counties record measurable tornado risk in FEMA's National Risk Index; 8 of them are rated High or Very High.

Other Hazards in Iowa

Cold Wave Drought Earthquake Hail Heat Wave Hurricane Ice Storm Riverine Flood Landslide Lightning Strong Wind Wildfire Winter Weather