Stephenson County, Illinois
County storm and disaster record · FIPS 17177 · population 44,602 · 564 sq mi
NOAA's Storm Events Database holds 756 records for Stephenson County, Illinois from 1950 through June 30, 2026, on 460 days; the most frequent are severe thunderstorm wind events (264 records). The deadliest single record is the July 27, 2011 flash flood: 2 deaths and $656,000 in damage in 2025 dollars. FEMA has issued 14 declarations naming the county since 1969, 12 of them for natural hazards; the latest for a natural hazard was “Severe Storms and Flooding” on September 19, 2019.
The record, 1950 to 2026
Storm records filed for the county each year (2026 to June 30, 2026). Before 1996 NOAA recorded only tornadoes (from 1950), thunderstorm wind and hail (from 1955).
- recorded, no damage figure
- under $100,000
- $100,000 or more
- $1 million or more
- $10 million or more, or a death
- $100 million or more, or 10 deaths
- a year's colour: its recorded damage or deaths
- a year with a death
- 1955: wind and hail recorded from 1955
- 1996: all 48 event types from 1996
- Storm records
- 756on 460 days, 1950 to June 30, 2026
- Deaths recorded
- 24 injuries
- Damage, 2025 dollars
- $86Mas filed (scale steps before 1993)
- Tornadoes
- 23strongest EF2
- FEMA declarations
- 14latest 2020
Source: NOAA NCEI Storm Events Database, records through June 30, 2026 (file revision 20260918); damage converted to 2025 dollars with the BLS CPI-U. Search the record at NCEI. BLS consumer price index.
What hazards hit Stephenson County most?
The most frequent records are severe thunderstorm wind events: 264 since 1956. 57% of its severe thunderstorm wind events since 1956 fell in June and July. The rank column places the county among Illinois's counties by days with a record per 1,000 square miles of land over each hazard's complete period.
| Hazard | Records | Days | First, last | Killed | Injured | Damage | Rank in state |
|---|---|---|---|---|---|---|---|
| Severe thunderstorm wind | 264 | 142 | 1956-2026 | 0 | 4 | $8.1M | 45 of 102 |
| Winter storms | 161 | 160 | 1996-2026 | 0 | 0 | $32K | 17 of 102 |
| Hail | 135 | 70 | 1972-2026 | 0 | 0 | $428K | 56 of 102 |
| Floods | 57 | 37 | 1997-2026 | 2 | 0 | $13M | 69 of 102 |
| Heavy rain | 31 | 10 | 2003-2011 | 0 | 0 | $37K | 23 of 102 |
| Extreme cold | 24 | 23 | 1996-2019 | 0 | 0 | $37K | 36 of 102 |
| Tornadoes | 23 | 18 | 1958-2026 | 0 | 0 | $28M | 91 of 102 |
| Fog, smoke and funnel clouds | 22 | 19 | 1998-2022 | 0 | 0 | – | 24 of 102 |
| High wind and dust storms | 17 | 15 | 1996-2016 | 0 | 0 | $5.0M | 53 of 102 |
| Drought | 13 | 13 | 2005-2012 | 0 | 0 | $32M | 56 of 102 |
| Lightning | 5 | 5 | 1999-2018 | 0 | 0 | $98K | 26 of 102 |
| Heat | 4 | 4 | 1997-2013 | 0 | 0 | – | 97 of 102 |
Source: NOAA NCEI Storm Events Database (county and forecast-zone records attributed to the county; a zone record shows its own totals on each county it covers). Days: dates with at least one record of the hazard in the county. Ranks: days with a record per 1,000 square miles of land (Census Bureau 2024 Gazetteer), since 1950 for tornadoes, 1955 for hail and thunderstorm wind, 1996 for the rest.
How many tornadoes has Stephenson County had?
NOAA records 23 tornadoes in Stephenson County from 1958 to 2026, the strongest rated EF2, with 0 deaths and 0 injuries recorded in the county. A tornado that crossed a county line is counted in each county it touched, with the length of its path inside the county.
Counted as whole tornadoes rather than county records, the Storm Prediction Center's database holds 21 tornadoes whose track touched Stephenson County since 1950 (NOAA's county records number 23: they file a crossing tornado once per county segment, and the two databases differ on some tracks); along their whole tracks they killed 1 person, 0 of them in Stephenson County.
| Date | Tornado | Rating | Path | Killed |
|---|---|---|---|---|
| 1958-10-08 23:30, as SPC files it | Machesney Park to Waukegan | F2 | 81 mi | 1 |
Map of the strongest tornado tracks in Illinois.
Every tornado record filed for Stephenson County (23)
| Date | Place | Character | Killed | Injured | Damage |
|---|---|---|---|---|---|
| 2026-04-17 | Lena, Stephenson County | EF2 12.54 mi x 1,250 yd | 0 | 0 | – |
| 2026-04-14 | Pearl City, Stephenson County | EF1 5.08 mi x 100 yd | 0 | 0 | – |
| 2024-07-15 | Waddams Grove, Stephenson County | EFU 6.33 mi x 20 yd | 0 | 0 | – |
| 2024-07-15 | Dakota Dornink Airport, Stephenson County | EFU 1.01 mi x 10 yd | 0 | 0 | – |
| 2024-03-04 | Bolton, Stephenson County | EFU 0.1 mi x 30 yd | 0 | 0 | – |
| 2023-03-31 | Florence, Stephenson County | EFU 1 mi x 50 yd | 0 | 0 | – |
| 2022-05-25 | Oakdale Nature Prsrve, Stephenson County | EF1 1.83 mi x 30 yd | 0 | 0 | – |
| 2020-08-10 | Florence, Stephenson County | EF0 4.59 mi x 50 yd | 0 | 0 | – |
| 2017-08-16 | Sciota Mills, Stephenson County | EF0 3.25 mi x 20 yd | 0 | 0 | – |
| 2017-08-16 | Bolton, Stephenson County | EF1 2.79 mi x 75 yd | 0 | 0 | – |
| 2010-07-12 | Rock Grove, Stephenson County | EF0 0.07 mi x 25 yd | 0 | 0 | – |
| 2009-06-01 | Buena Vista, Stephenson County | EF0 0.33 mi x 200 yd | 0 | 0 | $138K |
| 2003-06-14 | German Vly, Stephenson County | F0 | 0 | 0 | $2K |
| 2003-06-14 | Florence, Stephenson County | F0 0.5 mi x 50 yd | 0 | 0 | $24K |
| 2003-06-14 | German Vly, Stephenson County | F0 | 0 | 0 | $2K |
| 1999-06-06 | Freeport, Stephenson County | F0 0.1 mi x 10 yd | 0 | 0 | – |
| 1999-06-01 | Florence, Stephenson County | F0 0.1 mi x 10 yd | 0 | 0 | – |
| 1998-08-24 | Pearl City, Stephenson County | F1 0.5 mi x 50 yd | 0 | 0 | $145K |
| 1998-05-28 | Eleroy, Stephenson County | F0 0.1 mi x 1 yd | 0 | 0 | $2K |
| 1998-05-28 | Lena, Stephenson County | F0 0.1 mi x 0 yd | 0 | 0 | – |
| 1971-06-01 | Stephenson County | F1 | 0 | 0 | $250K step |
| 1959-04-17 | Stephenson County | F1 2 mi x 33 yd | 0 | 0 | $25K step |
| 1958-10-08 | Stephenson County | F2 38.1 mi x 33 yd | 0 | 0 | $2.5M step |
A damage figure marked "step" is a record from before 1993: NOAA then filed damage by category, and the figure is the category as entered, in the dollars of that year, not an estimate of the loss.
Source: NOAA NCEI Storm Events Database, tornado records by county (path length in the county, maximum width); ratings as published: F scale before February 1, 2007, EF scale after. Whole-track figures: NOAA Storm Prediction Center tornado database (1950-2025). SPC severe weather database.
When was the last damaging storm in Stephenson County?
The most recent record with damage, injuries or deaths is the July 22, 2017 flood ($9.0 million in damage in 2025 dollars).
Heavy rainfall of 3 to over 12 inches over significant areas from 20 to 22 July in southern Wisconsin and Northern Illinois moved downstream causing the Rock River to rise well above major flood stage levels just downstream of Freeport down to the Mississippi at Moline. Freeport rose just below major flood stage level of 16.0 feet on July 23rd, 2017 at approximately 645 AM CST. It crested around 15.9 feet at approximately 10 AM CST on July 23rd, 2017 and fell below 15.5 feet at approximately 815 PM CST on July 25th. Widespread river flooding and flash flooding resulted in a preliminary estimation of 7 to 8 million dollars in damage.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 716606)
| Date | Record | Character | Killed | Injured | Damage |
|---|---|---|---|---|---|
| 2026-06-24 | Thunderstorm WindRock Grove, Stephenson County | 52 kt wind | 0 | 0 | – |
| 2026-06-11 | Flash FloodDamascus, Stephenson County | 0 | 0 | – | |
| 2026-06-10 | Thunderstorm WindLake Summerset, Stephenson County | 52 kt wind | 0 | 0 | – |
| 2026-06-10 | Thunderstorm WindCedarville, Stephenson County | 50 kt wind | 0 | 0 | – |
| 2026-04-17 | TornadoLena, Stephenson County | EF2 12.54 mi x 1,250 yd | 0 | 0 | – |
| 2026-04-17 | HailDakota, Stephenson County | 1.75 in hail | 0 | 0 | – |
| 2026-04-17 | HailWinneshiek, Stephenson County | 1.00 in hail | 0 | 0 | – |
| 2026-04-17 | HailWinneshiek, Stephenson County | 1.00 in hail | 0 | 0 | – |
| 2026-04-17 | HailWinneshiek, Stephenson County | 1.75 in hail | 0 | 0 | – |
| 2026-04-17 | HailDakota, Stephenson County | 2.75 in hail | 0 | 0 | – |
| 2026-04-17 | HailLake Summerset, Stephenson County | 2.00 in hail | 0 | 0 | – |
| 2026-04-17 | HailRock Grove, Stephenson County | 1.75 in hail | 0 | 0 | – |
Source: NOAA NCEI Storm Events Database; every record of 2025-2026 is listed, earlier ones when they caused deaths, injuries or $250,000 of damage (2025 dollars), and every tornado.
The deadliest and costliest records
| Date | Record | Character | Killed | Injured | Damage |
|---|---|---|---|---|---|
| 2011-07-27 | Flash FloodWaddams Grove, Stephenson County Torrential rains of 3 to 8 inches caused some flash flooding across parts of Stephenson County during the evening of July 27 and morning of July 28. There were reports of cattle scattered through county by flood waters with some washed downstream. The flood waters were several feet deep in the town of Pearl City. Two ... | 2 | 0 | $656K | |
| 2008-07-31 | Thunderstorm WindWinslow, Stephenson County Wind gusts estimated to be 70 mph blew down a pole barn on State Line Rd and Swiss Rd near Winslow, IL at 12:35 pm July 31. One person was injured with several fractures. | 61 kt wind | 0 | 1 | $34K |
| 2003-07-05 | Thunderstorm WindPearl City, Stephenson County Limb down on a tent | 55 kt wind | 0 | 1 | $48K |
| 1999-05-16 | Thunderstorm WindOrangeville, Stephenson County Severe thunderstorm winds rolled a mobile home trailer over and destroyed it. The occupant of the trailer suffered 2 dislocated shoulders, cuts, and abrasions. | 0 | 1 | $71K | |
| 1987-08-16 | Thunderstorm WindStephenson County | 0 | 1 | – |
| Date | Record | Character | Killed | Injured | Damage |
|---|---|---|---|---|---|
| 2005-07-01 | DroughtStephenson County · forecast zone Stephenson | 0 | 0 | $27M | |
| 2017-07-22 | FloodWinslow, Stephenson County | 0 | 0 | $9.0M | |
| 2005-08-01 | DroughtStephenson County · forecast zone Stephenson | 0 | 0 | $4.9M | |
| 2003-07-05 | Thunderstorm WindCountywide, Stephenson County | 61 kt wind | 0 | 0 | $4.1M |
| 2003-05-09 | High WindStephenson County · forecast zone Stephenson | 65 kt wind | 0 | 0 | $3.2M |
| 1996-04-19 | Thunderstorm WindPearl City, Stephenson County | 0 | 0 | $2.3M | |
| 2010-07-22 | Flash FloodWaddams Grove, Stephenson County | 0 | 0 | $1.4M | |
| 2010-07-24 | FloodWinslow, Stephenson County | 0 | 0 | $677K |
Before 1993 NOAA filed damage by category, not amount, so the list above starts in 1993. The highest category filed here before then (entered as $2.5M, in the dollars of the day) holds: October 8, 1958 (tornado, Stephenson County).
Source: NOAA NCEI Storm Events Database: deaths and injuries direct and indirect; damage is property plus crops as estimated by the National Weather Service, converted to 2025 dollars.
Is it getting more frequent?
Records per decade for Stephenson County's most frequent hazards. Counts rose everywhere after 1996, when NOAA began recording every event type, so compare decades within a hazard's complete period only (the shaded cells come before it).
| Hazard | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020-26 |
|---|---|---|---|---|---|---|---|---|
| Severe thunderstorm wind | 1 | 3 | 15 | 17 | 26 | 83 | 70 | 49 |
| Winter storms | – | – | – | – | 19 | 71 | 51 | 20 |
| Hail | 0 | 0 | 7 | 4 | 9 | 45 | 38 | 32 |
| Floods | – | – | – | – | 3 | 22 | 24 | 8 |
| Heavy rain | – | – | – | – | 0 | 13 | 18 | 0 |
| Extreme cold | – | – | – | – | 4 | 13 | 7 | 0 |
Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).
What time of year?
57% of its severe thunderstorm wind events since 1956 fell in June and July. The two busiest months are in violet.
The values, month by month
Jan 58 · Feb 52 · Mar 39 · Apr 72 · May 63 · Jun 144 · Jul 124 · Aug 90 · Sep 22 · Oct 13 · Nov 18 · Dec 61 (records).
Source: NOAA NCEI Storm Events Database, records by the month they began.
Federal disaster declarations for Stephenson County
FEMA's register lists 14 declarations that include Stephenson County: 9 major disasters, 5 emergencies and 0 fire management assistance declarations. Most were for flood (4) and snowstorm (4).
| Declared | Number | Type | Title |
|---|---|---|---|
| 2020-03-26 | DR-4489 | Biological | Covid-19 Pandemic |
| 2020-03-13 | EM-3435 | Biological | Covid-19 |
| 2019-09-19 | DR-4461 | Flood | Severe Storms and Flooding |
| 2011-03-17 | DR-1960 | Snowstorm | Severe Winter Storm and Snowstorm |
| 2010-08-19 | DR-1935 | Severe Storm | Severe Storms and Flooding |
| 2008-03-13 | EM-3283 | Snowstorm | Record Snow and Near Record Snow |
| 2007-08-30 | DR-1722 | Severe Storm | Severe Storms and Flooding |
| 2006-12-29 | EM-3269 | Snowstorm | Snow |
| 2005-09-07 | EM-3230 | Hurricane | Hurricane Katrina Evacuation |
| 1996-07-25 | DR-1129 | Severe Storm | Severe Storms and Flooding |
| 1993-07-09 | DR-997 | Flood | Severe Storms & Flooding |
| 1979-01-16 | EM-3068 | Snowstorm | Blizzards & Snowstorms |
| 1974-06-10 | DR-438 | Flood | Severe Storms & Flooding |
| 1969-08-30 | DR-276 | Flood | Heavy Rains & Flooding |
Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), declarations through October 2, 2026; one declaration is counted once however many areas it names. OpenFEMA dataset page.
How many floods has Stephenson County had?
NOAA's Storm Events Database holds 57 flood or flash flood records for Stephenson County from 1997 to 2026, on 37 days, with 2 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Stephenson County ranks 956th of 2,942 U.S. counties.
The National Flood Insurance Program has paid $3.6 million on 193 claims filed in Stephenson County; the most in one year was 35 in 2017. Claims count insured losses only: uninsured flood damage is not in this file.
The values, year by year
1979: 3 · 1980: 1 · 1982: 3 · 1983: 1 · 1985: 3 · 1990: 8 · 1993: 15 · 1995: 1 · 1996: 5 · 1997: 9 · 2000: 9 · 2002: 3 · 2004: 3 · 2007: 4 · 2008: 4 · 2009: 1 · 2010: 28 · 2011: 1 · 2013: 2 · 2017: 35 · 2018: 11 · 2019: 26 · 2020: 1 · 2022: 14 · 2024: 1 · 2026: 1; the other years: 0.
Source: FEMA OpenFEMA NFIP Redacted Claims, as of September 8, 2026; claims by year of loss, payments in the dollars of the year paid. OpenFEMA dataset page.
FEMA's modeled risk for Stephenson County
FEMA's National Risk Index rates Stephenson County Relatively Low overall, with an expected annual loss of $28.9 million. These are FEMA's model estimates of future loss from 18 hazards, not a count of what happened; they can differ from the record above.
| Hazard | Risk rating | Expected annual loss | Modeled frequency |
|---|---|---|---|
| Strong Wind | Relatively High | $1.4M | 5.1 a year (modeled) |
| Hail | Relatively Moderate | $2.1M | 3.6 a year (modeled) |
| Tornado | Relatively Moderate | $3.9M | once in about 2 years (modeled) |
| Drought | Relatively Moderate | $878K | 11 modeled event-days a year |
| Cold Wave | Relatively Moderate | $3.4M | 6.3 a year (modeled) |
| Riverine Flooding | Relatively Moderate | $16M | 1.3 a year (modeled) |
| Ice Storm | Relatively Moderate | $191K | about once a year (modeled) |
| Heat Wave | Relatively Low | $610K | 4.7 modeled event-days a year |
Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.
Counties that share a border with Stephenson County
Source: U.S. Census Bureau county adjacency file; NOAA NCEI Storm Events Database, records since 1950. The Census Bureau's adjacency file.
Next
- Tornadoes in IllinoisEvery Illinois tornado since 1950 and the counties with the most per square mile
- Severe thunderstorm wind in IllinoisThe state's severe thunderstorm wind events, by county, year and month
- The Illinois recordEvery hazard in the state, its deadliest events and its federal declarations
- FEMA's risk rating for each hazard in Stephenson CountyThe hazard risk calculator: 18 hazards beside the county's record
- Download Stephenson County's FEMA declarations (CSV)14 rows: every declaration that named the county, for your own analysis