Cook County, Illinois

What hazards hit Cook County most?

The most frequent records are severe thunderstorm wind events: 1,514 since 1955. 55% of its severe thunderstorm wind events since 1955 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.

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 Cook County had?

NOAA records 87 tornadoes in Cook County from 1954 to 2026, the strongest rated F4, with 39 deaths and 777 injuries recorded in the county. That is 25th of 102 Illinois counties by days with tornadoes per 1,000 square miles since 1950. 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 87 tornadoes whose track touched Cook County since 1950 (NOAA's county records number 87, the same count); along their whole tracks they killed 41 people, 39 of them in Cook County.

Map of the strongest tornado tracks in Illinois.

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 Cook County?

The most recent record with damage, injuries or deaths is the June 13, 2026 thunderstorm wind (1 injury).

Several large trees were blown down and uprooted near Burnham Avenue between 154th and 158th Streets. Some of the trees fell onto homes. One massive tree was uprooted and fell onto a house near 156th Street and Green Bay Avenue trapping a woman inside her house. She was transported to a local hospital. Tree limbs and power lines were also blown down.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 1333798)

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

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: 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 Cook 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).

Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).

What time of year?

55% of its severe thunderstorm wind events since 1955 fell in June and July. The two busiest months are in violet.

Source: NOAA NCEI Storm Events Database, records by the month they began.

Federal disaster declarations for Cook County

FEMA's register lists 24 declarations that include Cook County: 19 major disasters, 5 emergencies and 0 fire management assistance declarations. Most were for flood (8) and severe storm (8).

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 Cook County had?

NOAA's Storm Events Database holds 423 flood or flash flood records for Cook County from 1996 to 2026, on 211 days, with 3 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Cook County ranks 28th of 2,942 U.S. counties. The 100 counties with the most claims

The National Flood Insurance Program has paid $140 million on 15,260 claims filed in Cook County; the most in one year was 2,048 in 2008. Claims count insured losses only: uninsured flood damage is not in this file.

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 Cook County

FEMA's National Risk Index rates Cook County Very High overall, with an expected annual loss of $2.4 billion. 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.

Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.

Counties that share a border with Cook County

1. Cook County 3,347
2. Will County 1,579
3. DuPage County 1,203
4. Kane County 1,147
5. McHenry County 941
6. Lake County 869
7. Lake County, IN 866
8. Berrien County, MI 746
9. Porter County, IN 633

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 Cook CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Cook County's FEMA declarations (CSV)24 rows: every declaration that named the county, for your own analysis