Updated May 2026
Flood Risk in Illinois
Illinois carries a relatively low statewide average risk score of 10, with 100% of its 103 counties at A or B. 0 counties are in the F (extreme) tier, typically along major rivers or flood-prone basins. Statewide NFIP take-up is modest at 871 total claims.
Grade Distribution Across Illinois
The grade mix is dominated by A — 100% of counties — meaning the typical place in this state has very low historical flood loss. The handful of B/C/D/F counties below define where risk is concentrated.
How Illinois Compares Nationally
The U.S. county-level average composite score is 12. Illinois sits at 10, which is right around the national average. 427 federal flood-related disaster declarations across 103 counties — averaging 4.1 per county, well above the U.S. norm. The state experiences large-loss flood events on a recurring basis.
For full national context — every state ranked by average score and total claims — see the all-states overview. The riskiest-counties ranking and highest-payouts ranking drill into where loss is concentrated. Real-time stream-gauge readings are at USGS Water Data.
Riskiest in Illinois
| County | Grade | Score |
|---|---|---|
| Rock Island | A | 20 |
| St. Clair | A | 18 |
| Winnebago | A | 18 |
| McHenry | A | 18 |
| Kane | A | 16 |
Safest in Illinois
| County | Grade | Score |
|---|---|---|
| Lake | A | 5 |
| Will | A | 7 |
| Madison | A | 8 |
| Stephenson | A | 8 |
| Cook | A | 8 |
How Illinois's Risk Is Calculated
Every county in Illinois is scored on the same four factors that drive every county nationwide: NFIP claims density (40%), federally declared flood-disaster frequency (25%), average claim severity (20%), and year-over-year trend (15%). Source data comes from the public FEMA flood-mapping program and OpenFEMA endpoints. Detailed weighting math, plus the data's known limitations (county-level granularity, NFIP-participation bias, historical bias), is on the methodology page.
All 103 Counties in Illinois
Sorted by flood risk score, highest to lowest.
| # | County | Grade | Score | Claims | Payouts | Disasters |
|---|---|---|---|---|---|---|
| 1 | Rock Island | A | 20 | 46 | $1,099,365 | 10 |
| 2 | St. Clair | A | 18 | 54 | $526,136 | 9 |
| 3 | Winnebago | A | 18 | 23 | $780,629 | 6 |
| 4 | McHenry | A | 18 | 24 | $289,397 | 6 |
| 5 | Kane | A | 16 | 9 | $67,652 | 5 |
| 6 | Calhoun | A | 14 | 21 | $322,242 | 12 |
| 7 | Jersey | A | 14 | 29 | $943,964 | 10 |
| 8 | Adams | A | 13 | 6 | $179,542 | 10 |
| 9 | Pike | A | 13 | 5 | $258,724 | 11 |
| 10 | Carroll | A | 12 | 3 | $3,109 | 8 |
| 11 | Cass | A | 12 | 1 | $145 | 8 |
| 12 | Fulton | A | 12 | 1 | $74,211 | 9 |
| 13 | Hancock | A | 12 | 1 | $39,371 | 9 |
| 14 | Henderson | A | 12 | 6 | $71,874 | 9 |
| 15 | Mercer | A | 12 | 0 | $0 | 8 |
| 16 | Monroe | A | 12 | 3 | $35,704 | 9 |
| 17 | Whiteside | A | 12 | 7 | $101,264 | 8 |
| 18 | Grundy | A | 12 | 10 | $303,788 | 5 |
| 19 | Tazewell | A | 12 | 6 | $57,119 | 6 |
| 20 | Alexander | A | 11 | 7 | $68,595 | 7 |
| 21 | Bureau | A | 11 | 0 | $0 | 7 |
| 22 | Greene | A | 11 | 1 | $15,000 | 7 |
| 23 | Henry | A | 11 | 0 | $0 | 7 |
| 24 | Jackson | A | 11 | 1 | $3,410 | 6 |
| 25 | Morgan | A | 11 | 3 | $217,854 | 7 |
| 26 | Randolph | A | 11 | 4 | $47,073 | 7 |
| 27 | Schuyler | A | 11 | 0 | $0 | 7 |
| 28 | Scott | A | 11 | 0 | $0 | 6 |
| 29 | Union | A | 11 | 3 | $7,408 | 6 |
| 30 | Brown | A | 11 | 1 | $22,209 | 6 |
| 31 | La Salle | A | 11 | 4 | $26,334 | 7 |
| 32 | Mason | A | 11 | 6 | $81,832 | 7 |
| 33 | Jo Daviess | A | 11 | 1 | $20,450 | 7 |
| 34 | Knox | A | 10 | 2 | $0 | 5 |
| 35 | Lee | A | 10 | 0 | $0 | 5 |
| 36 | Ogle | A | 10 | 2 | $18,608 | 5 |
| 37 | DeKalb | A | 10 | 2 | $0 | 4 |
| 38 | Clark | A | 10 | 0 | $0 | 4 |
| 39 | DuPage | A | 10 | 30 | $589,646 | 5 |
| 40 | Kendall | A | 10 | 1 | $17,254 | 4 |
| 41 | Marshall | A | 10 | 2 | $7,564 | 5 |
| 42 | Woodford | A | 10 | 7 | $203,898 | 5 |
| 43 | Pulaski | A | 10 | 3 | $55,294 | 5 |
| 44 | Lawrence | A | 9 | 3 | $19,622 | 2 |
| 45 | Shelby | A | 9 | 0 | $0 | 2 |
| 46 | Douglas | A | 9 | 6 | $81,035 | 2 |
| 47 | Crawford | A | 9 | 0 | $0 | 3 |
| 48 | Livingston | A | 9 | 2 | $4,492 | 3 |
| 49 | McDonough | A | 9 | 0 | $0 | 2 |
| 50 | Putnam | A | 9 | 1 | $27,315 | 3 |
| 51 | Stark | A | 9 | 0 | $0 | 2 |
| 52 | Warren | A | 9 | 0 | $0 | 3 |
| 53 | Boone | A | 9 | 3 | $20,028 | 3 |
| 54 | Clinton | A | 9 | 2 | $76,000 | 3 |
| 55 | Coles | A | 9 | 1 | $0 | 2 |
| 56 | Cumberland | A | 9 | 0 | $0 | 2 |
| 57 | De Witt | A | 9 | 0 | $0 | 2 |
| 58 | Edgar | A | 9 | 0 | $0 | 2 |
| 59 | Franklin | A | 9 | 0 | $0 | 2 |
| 60 | Gallatin | A | 9 | 0 | $0 | 2 |
| 61 | Johnson | A | 9 | 0 | $0 | 2 |
| 62 | Kankakee | A | 9 | 27 | $986,007 | 2 |
| 63 | Logan | A | 9 | 0 | $0 | 3 |
| 64 | McLean | A | 9 | 6 | $163,719 | 2 |
| 65 | Macon | A | 9 | 1 | $0 | 3 |
| 66 | Massac | A | 9 | 2 | $319,102 | 3 |
| 67 | Menard | A | 9 | 0 | $0 | 2 |
| 68 | Pope | A | 9 | 0 | $0 | 3 |
| 69 | Sangamon | A | 9 | 2 | $66,712 | 2 |
| 70 | Washington | A | 9 | 1 | $40,893 | 2 |
| 71 | Statewide | A | 9 | 0 | $0 | 2 |
| 72 | Madison | A | 8 | 37 | $444,901 | 6 |
| 73 | Stephenson | A | 8 | 12 | $304,310 | 5 |
| 74 | Cook | A | 8 | 198 | $1,891,708 | 9 |
| 75 | Peoria | A | 8 | 24 | $186,357 | 6 |
| 76 | Bond | A | 8 | 1 | $85,275 | 1 |
| 77 | Champaign | A | 8 | 2 | $22,496 | 1 |
| 78 | Christian | A | 8 | 1 | $30,748 | 1 |
| 79 | Clay | A | 8 | 1 | $7,013 | 1 |
| 80 | Edwards | A | 8 | 0 | $0 | 1 |
| 81 | Effingham | A | 8 | 0 | $0 | 1 |
| 82 | Fayette | A | 8 | 0 | $0 | 1 |
| 83 | Ford | A | 8 | 1 | $2,437 | 1 |
| 84 | Hamilton | A | 8 | 0 | $0 | 1 |
| 85 | Hardin | A | 8 | 0 | $0 | 1 |
| 86 | Iroquois | A | 8 | 68 | $1,547,467 | 1 |
| 87 | Jasper | A | 8 | 0 | $0 | 1 |
| 88 | Jefferson | A | 8 | 0 | $0 | 1 |
| 89 | Macoupin | A | 8 | 0 | $0 | 1 |
| 90 | Marion | A | 8 | 0 | $0 | 1 |
| 91 | Montgomery | A | 8 | 1 | $8,082 | 1 |
| 92 | Moultrie | A | 8 | 1 | $0 | 1 |
| 93 | Perry | A | 8 | 1 | $16,242 | 1 |
| 94 | Piatt | A | 8 | 0 | $0 | 1 |
| 95 | Richland | A | 8 | 0 | $0 | 1 |
| 96 | Saline | A | 8 | 1 | $4,293 | 1 |
| 97 | Vermilion | A | 8 | 7 | $388,530 | 1 |
| 98 | Wabash | A | 8 | 0 | $0 | 1 |
| 99 | Wayne | A | 8 | 0 | $0 | 1 |
| 100 | White | A | 8 | 2 | $142,951 | 1 |
| 101 | Williamson | A | 8 | 2 | $13,931 | 1 |
| 102 | Will | A | 7 | 27 | $301,522 | 5 |
| 103 | Lake | A | 5 | 92 | $1,344,971 | 5 |
Frequently Asked Questions
What is the average flood risk score in Illinois?
Illinois's average composite flood risk score is 10 on a 0–100 scale, computed as the mean of all 103 county scores. That is roughly equal to the U.S. county-level average of 12. Score components: 40% claims density, 25% disaster frequency, 20% claim severity, 15% trend.
Which counties in Illinois have the highest flood risk?
The riskiest county in Illinois is Rock Island with a composite score of 20 (grade A). The next four — St. Clair, Winnebago, McHenry, Kane — round out the top-five most exposed places in the state.
How many NFIP flood-insurance claims has Illinois filed?
FEMA's National Flood Insurance Program shows 871 claims on file from Illinois, with combined payouts of $15,104,824 across the dataset. 68 of the state's 103 counties have at least one NFIP claim recorded.
Are FEMA flood maps the same as your risk score?
No. The flood risk score on this page is a county-wide composite drawn from claims, disasters, severity, and trend. FEMA Flood Insurance Rate Maps (FIRMs, available at fema.gov/flood-maps) are parcel-level zone designations based on hydrologic modeling. The two answer different questions; serious decisions about insurance or building should use both, plus real-time hydrology from USGS Water Data.
When was the Illinois data last updated?
These figures were refreshed from the OpenFEMA API on 2026-05-16. FEMA itself publishes new NFIP claims on a quarterly cycle, so the data may lag actual events by up to three months.
Flood risk profile for Illinois: 103 counties, 871 NFIP claims, average composite score 10.
For this entity, the underlying data on this page comes from FEMA OpenFEMA datasets including the National Flood Hazard Layer and NFIP claims. The breakdown above is the federal record; the paragraphs below add the per-entity context that makes the headline numbers usable for a real decision rather than just a data lookup.
Every number on this page links back to FEMA OpenFEMA datasets including the National Flood Hazard Layer and NFIP claims; the methodology page describes the inputs, refresh cadence, and known limitations of the underlying data product.
For readers using this page as a decision input, the related-entity pages elsewhere on the site provide the comparison set. The most useful comparison for this entity is typically a peer within U.S. ZIPs, counties, and states with similar size, similar exposure, or similar geography — not the national-level summary alone.