Cook County, IL flood risk and natural hazards
FEMA rates riverine flooding, tornado and heat wave risk as Very High in Cook County, IL. Modeled losses from natural hazards (expected annual loss) average about $2.4 billion a year, for a population of 5,272,775. These county figures come from the FEMA National Risk Index, December 2025 release. Observation windows vary by metric and sit beside the tables below.
- Modeled expected annual loss
- $2.42 billion / year
- US loss rank
- #2 of 3,232
- State loss rank
- #1 of 102
- Loss per resident
- $460 · state $501 · US $459
- FEMA overall risk rating
- Very High
Illinois county modeled loss
- Positive estimates to $8.8 million
- Above $8.8 million to $13.7 million
- Above $13.7 million to $22.6 million
- Above $22.6 million to $47.4 million
- Above $47.4 million to $2.42 billion
- No FEMA estimate
Cook County, IL ranks #1 of 102 in the state for modeled expected annual loss; the outline locates it.
View chart data
Is Cook County at risk of flooding?
FEMA labels riverine flooding Very High and coastal flooding Relatively Low. Modeled annual riverine flood loss is $1,096,923,384; coastal flood loss is $36,524. These are separate hazards and county totals. A rating describes relative county risk. It does not locate water at a building or establish a flood zone. Read missing statuses using the source documentation. Keep both source labels when comparing counties. Read the county rating versus flood-zone guide before requesting a location check.
Look up an address and its flood zone through FEMA’s Flood Map Service Center.
The local hazard planning document is Cook County Multi-Jurisdictional Hazard Mitigation Plan. Local governments use this plan to set out hazards and proposed projects.
What natural hazards affect Cook County most?
Show tabular data
| County | Modeled expected annual loss (USD/year) | Overall risk rating |
|---|---|---|
| Cook County, IL | 2,424,304,449.02 | Very High |
Show tabular data
| Hazard | Source label | Observation window |
|---|---|---|
| Coastal flooding | Relatively Low | 1996-2023 |
| Riverine flooding | Very High | 1996-2023 |
| Hurricane | Very Low | 1851-2024 |
| Wildfire | Very Low | 1996-2023 |
| Earthquake | Relatively High | 1996-2023 |
| Tornado | Very High | 1950-2023 |
| Heat wave | Very High | 2005-2024 |
How have heat and rain changed in Cook County?
Hot days
Hot days round to 0.0 in both decades; hollow marks confirm the zero state.
View chart data
| Place | Days / year |
|---|---|
| 1991–2000 | 0.00 |
| 2016–2025 | 0.00 |
Warm nights
Warm nights increased between the two decades.
View chart data
| Place | Days / year |
|---|---|
| 1991–2000 | 0.20 |
| 2016–2025 | 1.40 |
Heavy-precipitation days
Heavy-precipitation days increased between the two decades.
View chart data
| Place | Days / year |
|---|---|
| 1991–2000 | 0.40 |
| 2016–2025 | 0.80 |
Humid-heat days
Humid-heat days decreased between the two decades.
View chart data
| Place | Days / year |
|---|---|
| 1991–2000 | 1.10 |
| 2016–2025 | 0.80 |
| Measure | 1991–2000 | 2016–2025 | Change |
|---|---|---|---|
| Hot days · ≥35°C (95°F) | 0.0 | 0.0 | 0.0 |
| Humid-heat days · heat index ≥103°F (39.4°C) | 1.1 | 0.8 | −0.3 |
| Warm nights · ≥24°C (75.2°F) | 0.2 | 1.4 | +1.2 |
| Heavy-rain days · ≥50 mm (≈2 in) | 0.4 | 0.8 | +0.4 |
| Annual maximum daily precipitation · mm | 44.8 | 55.5 | +10.7 |
Counts are days per year; a grid-cell zero does not mean the county had no such events. Thresholds, time bases and limits: county climate method.
Methodology & sensor cross-check notes
Hot-day cross-check: NOAA’s county-average daily maximum temperature gives 1.3 → 0.8 hot days a year (−0.5); NASA gives 0.0 → 0.0 (0.0). The series disagree: NASA shows no change, while NOAA shows a decrease. The footprints differ, so agreement does not validate either count. Warm nights and precipitation were not cross-checked. Humid-heat row: Copernicus (ECMWF) reanalysis. It uses a different regional grid from the NASA measures.
No statistical significance, cause or future trend is established; this does not change the FEMA ratings above.
Climate data: NASA · Population context: US Census Bureau · Hot-day cross-check: NOAA county climate records · Humid heat: Copernicus (ECMWF). Method, sources and limitations · Climate JSON · Data credits.
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direction"}}How does El Niño affect Cook County winters?
Strong El Niño winter precipitation
5 of 9 strong El Niño winters were wetter than normal. The vertical line marks 100% of normal precipitation.
View chart data
| Winter | Precipitation (% of normal) |
|---|---|
| 1957–58 | 63.299 |
| 1965–66 | 104.373 |
| 1972–73 | 94.772 |
| 1982–83 | 143.418 |
| 1991–92 | 66.624 |
| 1997–98 | 110.080 |
| 2009–10 | 91.310 |
| 2015–16 | 122.227 |
| 2023–24 | 114.740 |
NOAA and IRI both give 100% odds that El Niño conditions (tropical Pacific ONI of at least 0.5°C, not a local weather forecast) are present this winter. In Cook County, 5 of 9 past strong El Niño winters were wetter than normal; the median winter had 104% of normal precipitation (rain and melted snow). The driest, 1957–58, had 63%.
| Winter | ONI | Precipitation | Temp. | Heavy days | Claims |
|---|---|---|---|---|---|
| 1957–58 | 1.7 | 63% | +0.9°F | 0 | — |
| 1965–66 | 1.6 | 104% | +1.3°F | 2 | — |
| 1972–73 | 1.8 | 95% | +1.5°F | 0 | — |
| 1982–83 | 2.1 | 143% | +5.9°F | 1 | 551 (#1) |
| 1991–92 | 1.5 | 67% | +4.4°F | 0 | 3 (#29) |
| 1997–98 | 2.4 | 110% | +6.2°F | 0 | 2 (#37) |
| 2009–10 | 1.5 | 91% | −2.3°F | 0 | 1 (#44) |
| 2015–16 | 2.6 | 122% | +4.2°F | 2 | 6 (#22) |
| 2023–24 | 2.0 | 115% | +6.4°F | 0 | 7 (#21) |
Winter normals and temperature baseline
Cook County normals, 1990–91 to 2019–20 winters: 6.0 inches of precipitation (rain and melted snow) and 0.7 heavy days. Temperature is set against the county’s own winter trend of +0.6°F per decade since 1951–52.
Flood claims: December–February, from 1978 (— = before the data). The rank compares each winter with all 47 winters from 1978–79 to 2024–25 (#1 is the most claims; no rank is shown for 0 claims). The median winter had 4 claims; 3 of 6 strong winters in the data were above it. Insured exposure grew over time, so counts are not comparable across decades.
Past tendency is not a forecast and not a property-level finding. Before winter: four checks for property teams.
Sources: NOAA county climate records and Pacific climate assessments; FEMA National Flood Insurance Program claims. Method and limits · El Niño 2026–27.
What are the modeled losses by hazard?
From 1991–2000 to 2016–2025, hot days near Cook County changed from 0.0 to 0.0 per year. Heavy-rain days changed from 0.4 to 0.8. The table retains humid heat, warm nights and maximum daily rain. Compare the periods alongside the source notes. These decade means describe past conditions; they do not predict a future year or establish a trend.
Cook County’s modeled loss across all hazards is $2,424,304,449 per year. The FEMA National Risk Index ranks the hazards below by modeled loss, not rating category.
Show tabular data
| Hazard | Total loss ($/yr) | Of which buildings ($/yr) | Observation window |
|---|---|---|---|
| All hazards (composite) | $2,424,304,449 | $1,260,921,853 | 1996-2023 |
| Riverine flooding | $1,096,923,384 | $1,091,658,092 | 1996-2023 |
| Tornado | $344,681,902 | $115,295,853 | 1950-2023 |
| Heat wave | $193,392,334 | Not published | 2005-2024 |
| Earthquake | $57,293,394 | $38,319,105 | 1996-2023 |
| Hurricane | $56,776 | $56,472 | 1851-2024 |
| Wildfire | $56,110 | $47,700 | 1996-2023 |
| Coastal flooding | $36,524 | $34,851 | 1996-2023 |
These modeled county totals do not estimate property losses, insurance inputs or forecasts. Do not multiply them by location counts.
Reuse this chart
What is exposed in Cook County?
Population and asset values show the scale behind county losses. These county totals are exposure measures, not loss figures.
Show tabular data
| Measure | Value | Observation window |
|---|---|---|
| Resident population | 5,272,775 | 2020-2020 |
| Building replacement value | $1,002,575,627,463 | 2020-2020 |
| Agricultural market value | $25,352,865 | 2022-2022 |
What do vulnerability and resilience show?
These relative rankings describe susceptibility to hazard impacts and capacity to recover. They measure no individual asset or outcome.
Show tabular data
| Measure | Score | Observation window |
|---|---|---|
| Social vulnerability index | 61.7 | 2020-2020 |
| Community resilience index | 73.3 | 2020-2020 |
Cook County in the state and national rankings
National placement for Cook County is #2 of 3,232, with an expected annual loss estimate of about $2.42 billion. Its share of Illinois modeled loss is 37.8%, with a state rank of #1 of 102. About $2.42 billion is the modeled yearly average over the long run, rather than a one-year prediction. Only Los Angeles County, CA has more modeled loss, at about $7.60 billion annually. The next lower national total is about $2.27 billion, in Riverside County, CA. The next lower total within Illinois belongs to DuPage County, IL, at about $366.0 million. That puts the estimates about $2.06 billion apart, with 5.7% of state loss in the comparison county.
County hazard loss mix
Riverine Flood leads the modeled expected annual loss mix; bar lengths share a zero baseline.
View chart data
| Hazard | USD / year | Share |
|---|---|---|
| Riverine Flood | 1,096,923,384.30 | 45.2% |
| Cold Wave | 699,974,246.73 | 28.9% |
| Tornado | 344,681,901.52 | 14.2% |
| Heat Wave | 193,392,333.52 | 8.0% |
| Earthquake | 57,293,393.96 | 2.4% |
| Strong Wind | 11,628,974.43 | 0.5% |
| Other | 20,410,214.56 | 0.8% |
National hazard loss ranks
Riverine Flood ranks #5 of 3,232 by modeled expected annual loss. Higher percentiles mean larger modeled losses.
View chart data
| Hazard | Rank | Percentile |
|---|---|---|
| Riverine Flood | #5 of 3,232 US · #1 of 102 in IL | 99.88 |
| Cold Wave | #1 of 3,232 US · #1 of 102 in IL | 100.00 |
| Tornado | #3 of 3,225 US · #1 of 102 in IL | 99.94 |
| Heat Wave | #6 of 3,202 US · #1 of 102 in IL | 99.84 |
| Earthquake | #56 of 3,232 US · #1 of 102 in IL | 98.30 |
| Strong Wind | #18 of 3,225 US · #1 of 102 in IL | 99.47 |
Modeled loss per resident
Cook has about $460 in modeled expected annual loss per resident. State and US values divide total loss by total population.
View chart data
| Place | USD / resident / year |
|---|---|
| Cook | 459.78 |
| Illinois | 500.63 |
| US | 459.35 |
Cook County hazard estimates
Riverine Flood
FEMA models about $1.10 billion in expected annual loss from riverine flooding, placing the county #5 of 3,232 nationally. This hazard makes up 45.2% of the total; FEMA assigns a Very High rating, and its loss ranks #1 of 102 in Illinois; the Very High label covers 1 state county and 26 nationally for riverine flooding.
Cold Wave
The largest US county estimate for cold waves belongs here: about $700.0 million, ranking #1 of 3,232. In Illinois, this estimate ranks #1 of 102 and represents 28.9% of the county’s modeled loss; FEMA assigns a Very High rating; the Very High label covers 5 state counties and 39 nationally for cold waves.
Tornado
The national loss rank for tornadoes is #3 of 3,225, based on about $344.7 million in modeled expected annual loss. Its 14.2% share of total loss comes with a state loss rank of #1 of 102; FEMA assigns a Very High rating; the Very High label covers 4 state counties and 37 nationally for tornadoes.
Heat Wave
The national loss rank for heat waves is #6 of 3,202, based on about $193.4 million in modeled expected annual loss. In Illinois, this estimate ranks #1 of 102 and represents 8.0% of the county’s modeled loss; FEMA assigns a Very High rating, matching 11 US counties, including 1 in Illinois, for this hazard.
Earthquake
For earthquakes, about $57.3 million in expected annual loss puts the county #56 of 3,232 across the US. In Illinois, this estimate ranks #1 of 102 and represents 2.4% of the county’s modeled loss; FEMA assigns a Relatively High rating; for earthquakes, 1 state county and 53 US counties share that label.
Strong Wind
FEMA models about $11.6 million in expected annual loss from strong wind, placing the county #18 of 3,225 nationally. This hazard makes up 0.5% of the total; FEMA assigns a Very High rating, and its loss ranks #1 of 102 in Illinois; for strong wind, 5 state counties and 63 US counties share that label.
Between riverine flooding and cold waves, the modeled dollar gap is about $396.9 million; their shares differ by 16.4 percentage points. The loss estimate for cold waves exceeds tornadoes by about $355.3 million, equivalent to 14.7 percentage points of total loss. Between tornadoes and heat waves, the modeled dollar gap is about $151.3 million; their shares differ by 6.2 percentage points. For heat waves, modeled loss is about $136.1 million above earthquakes, leaving 5.6 percentage points between their county shares. For earthquakes, modeled loss is about $45.7 million above strong wind, leaving 1.9 percentage points between their county shares.
Population and recorded values
FEMA counts 5,272,775 residents in Cook County, across about 1,651 square miles. FEMA lists about $1,002.58 billion in building value. For agricultural value, the source records about $25.4 million. Per resident, the modeled annual amount is about $460; the Illinois average is about $501. The county holds 41.2% of the state population, compared with 37.8% of modeled loss. Buildings account for 33.3% of recorded Illinois building value. Among 102 state county records with both inputs, its density stands at position 1 from highest to lowest. The population-to-area ratio is about 3,193 residents per square mile; statewide it is about 219. The median county population in Illinois is about 25,382, compared with 5,272,775 locally. In the US totals, the county represents 1.6% of modeled annual loss and 1.6% of recorded residents. The county’s about $460 per resident compares with about $459 nationally in modeled annual loss. About $2.40 billion of annual loss falls within the six leading hazards, accounting for 99.2% of the total. The balance outside those six estimates is about $20.4 million, or 0.8% of total loss. The county’s number 7 hazard by dollar loss is hail: about $11.1 million, with a state rank of #1 of 102. With 0.5% of county loss, this hazard has national placement #41 of 3,225. The estimate for winter weather ranks #1 of 102 in Illinois: about $4.4 million annually, in local position 8. This 0.2% slice of county loss ranks #3 of 3,230 across US counties.
FEMA labels and risk score
Cook County has a FEMA risk index score of about 100.0, ranking #2 of 3,144 nationally. The risk index rating is Very High, a label shared by 1 of 102 Illinois counties. FEMA labels expected annual loss as Very High, matching 1 county records across Illinois. For social vulnerability, FEMA assigns Relatively High; 16 counties in Illinois have that label. Among 102 Illinois counties, 41 receive the same Relatively High label for community resilience. Its risk score ranks #1 of 102 within Illinois, while its loss total ranks #1 of 102. The Relatively High vulnerability and Relatively High resilience pairing appears in 6 Illinois counties. This county accounts for 96.5% of that group’s annual loss, while the group accounts for 39.2% across Illinois. The adjacent state score below this county belongs to DuPage County, IL: about 97.6, ranked #2 of 102. Its share of statewide modeled loss is 5.7%; FEMA’s risk index label there is Relatively High. FEMA lists 630 county records with Relatively High social vulnerability; together they contain 15.4% of its US population total. Across the US, this community resilience category, Relatively High, covers 24.5% of residents in 629 counties. FEMA assigns Very High to 8 hazards here, covering cold waves, heat waves, ice storms, lightning, riverine flooding, strong wind, tornadoes, winter weather. The county’s Relatively High group contains 2 hazards: earthquakes, hail. The county’s Relatively Low group contains 1 hazard: coastal flooding. FEMA assigns Very Low to 4 hazards here, covering drought, hurricanes, landslides, wildfires.
What else should I know about Cook County?
What does FEMA estimate for cold waves in Cook County?
Cook County has about $700.0 million in modeled expected annual loss from cold waves, with a Very High rating.
Which hazard has the largest modeled loss in Cook County?
Riverine flooding leads Cook County, at about $1.10 billion in modeled expected annual loss.
What building value does FEMA list for Cook County?
FEMA records about $1,002.58 billion of building value in Cook County.
What does FEMA estimate for hail in Cook County?
Cook County has about $11.1 million in modeled expected annual loss from hail, with a Relatively High rating.
What is the FEMA social vulnerability rating for Cook County?
FEMA assigns Cook County a Relatively High social vulnerability rating.
What is modeled loss per resident in Cook County?
Cook County averages about $460 per resident in modeled annual loss.
What share of state loss belongs to Cook County?
Cook County accounts for 37.8% of Illinois modeled expected annual loss.
Where next for Cook County?
See how the county compares across the state in Illinois natural hazard risk by county, download the FEMA county hazard data, or review the county climate risk data API and bulk files. Check the sources and what each measure can show on the methodology page.