DeKalb County, Illinois: Natural Disaster Risk and History
DeKalb County, Illinois has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 80.8 out of 100, higher than about 80% of US counties, with cold waves, tornadoes and inland (river and flash) flooding scoring highest of its 18 hazards and $47 million a year in expected losses.
OpenFEMA lists 10 federal disaster declarations that included DeKalb County since 1973, not counting 2 for COVID-19; the latest is DR-4116-IL (Severe Storms, Straight-Line Winds, and Flooding, declared 10 May 2013). NOAA's Storm Prediction Center recorded 30 tornadoes touching DeKalb County from 1950 to 2025.
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Population 100,385 Buildings worth $29 billion Area 641 sq mi Risk rank in Illinois 22 of 102 FIPS 17037
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Cold wave | Relatively High | 94.4 | $12 million | about 5.9 a year | 112 |
| Tornado | Relatively Moderate | 88.1 | $6.9 million | about once every 1.9 years | 21 |
| Inland flooding | Relatively Moderate | 83.0 | $24 million | about 1.1 a year | 32 |
| Strong wind | Relatively Moderate | 79.1 | $1.4 million | about 6.5 a year | 249 |
| Earthquake | Relatively Low | 75.8 | $1.3 million | about once every 719 years | — |
| Drought | Relatively Moderate | 74.7 | $751,568 | about 8.3 a year | 224 |
| Ice storm | Relatively Moderate | 60.1 | $146,599 | about once every 1.6 years | 42 |
| Heat wave | Relatively Low | 59.0 | $599,913 | about 3.4 a year | 55 |
| Lightning | Relatively Low | 50.1 | $252,507 | about 42 a year | 151,464 strikes |
| Hail | Relatively Low | 35.1 | $158,121 | about 4.6 a year | 174 |
| Winter weather | Relatively Low | 32.7 | $36,475 | about 15 a year | 285 |
| Landslide | Very Low | 28.7 | $304 | about once every 12 years | — |
| Hurricane | Very Low | 19.6 | $6,184 | about once every 113 years | 0 |
| Wildfire | Very Low | 6.4 | $2,203 | rarer than once in 1,000 years | — |
| Avalanche | Not Applicable | — | — | — | — |
| Coastal flooding | Not Applicable | — | — | — | — |
| Tsunami | Not Applicable | — | — | — | — |
| Volcanic activity | Not Applicable | — | — | — | — |
Score: FEMA's percentile among US counties that face the hazard (higher = more risk). Expected loss: FEMA's modelled average yearly loss to buildings, people (as a statistical value) and crops. How often: FEMA's annualised frequency of the hazard in the county; for some hazards it counts event-days, so it is a rough guide, not a forecast. "Not Applicable" means FEMA does not model that hazard here.
Federal disaster declarations 10
Most common: Flood 3, Snowstorm 3, Severe Storm 3, Hurricane 1.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 3 | Flood ×2, Snowstorm |
| 1990s | 1 | Severe Storm |
| 2000s | 4 | Severe Storm ×2, Snowstorm, Hurricane |
| 2010s | 2 | Flood, Snowstorm |
The last 10
Widest declarations that included DeKalb County
- Hurricane Katrina Evacuation (2005, EM-3230-IL): 102 Illinois counties designated.
- Severe Winter Storm and Snowstorm (2011, DR-1960-IL): 65 Illinois counties designated.
- Severe Storms & Flooding (1973, DR-373-IL): 52 Illinois counties designated.
Named storms in its declarations: Hurricane Katrina (2005).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Illinois also had 2 statewide declarations with no county list.
Tornado record since 1950 30
| Tornadoes touching the county | 30 |
|---|---|
| Strongest-rated | (E)F4 ×1 |
| Peak month | August (9) |
| Deadliest | 9 Apr 2015, EF4, 30.1 mi path, 2 killed, 11 injured |
| Longest path | 15 Aug 1958, F2, 74.5 mi path |
| Most recent | 15 Jul 2024, unrated, 1.8 mi path |
| Deaths / injuries on those paths | 2 / 12 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 17 | 7 | 2 | 0 | 1 | 0 | 3 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 2 | 1 | 3 | 1 | 1 | 4 | 4 | 14 |
Deaths and injuries are for each tornado's whole path, which can run beyond this county. F-scale ratings before February 2007, Enhanced Fujita (EF) after.
How DeKalb County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| DeKalb County (this page) | — | Relatively Low | 80.8 | Cold wave |
| Kane County | 29 km | Relatively High | 94.6 | Cold wave |
| Kendall County | 44 km | Relatively Low | 80.2 | Cold wave |
| Lee County | 47 km | Relatively Low | 54.4 | Strong wind |
| Boone County | 48 km | Relatively Low | 57.3 | Hail |
| Ogle County | 48 km | Relatively Low | 71.1 | Hail |
Nearest by distance between county centres. Every county in Illinois, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 29.2 |
|---|---|
| Community resilience | Relatively High 75.9 |
| Community risk factor | 0.96 |
| Expected annual loss, all hazards | $47 million |
FEMA scales expected losses up where social vulnerability is high (people who may find it harder to prepare, evacuate or recover) and down where community resilience is high. A factor above 1 raises the risk score. For social vulnerability a high rating is worse; for resilience a high rating is better.
Prepare for DeKalb County's main hazards
- Right now: National Weather Service alerts for Illinois · all official warnings on Global Incident Tracker.
- Cold wave: Carbon monoxide in winter · Power outages now
- Tornado: Is there a tornado warning now?
- Inland flooding: Flood safety: why shallow water kills · Floods recorded
- Your property's flood zone: FEMA Flood Map Service Center ↗ — this page cannot tell you that.
- Official preparedness guidance: Ready.gov ↗ and your county emergency management office.
What this page shows, and what it misses
FEMA's National Risk Index rates a whole county against every other US county; it is a planning-level estimate for nationwide comparison, not a flood-zone map and not a substitute for a local risk assessment or the risk to one home. Declarations are presidential disaster, emergency and fire management declarations that named this county; state declarations and SBA or USDA designations are not included. Tornadoes are counted when the county is one of up to four listed on the track; 670 tornadoes that crossed a state line carry no county list in NOAA's file and are left out.
Federal Emergency Management Agency (FEMA), National Risk Index Dataset: National Risk Index Counties - v1.20.0 (December 2025). Retrieved from https://services.arcgis.com/XG15cJAlne2vxtgt/ArcGIS/rest/services/National_Risk_Index_Counties/FeatureServer/0/query on November 2, 2026, 1:20 PM EST. This product uses the Federal Emergency Management Agency’s National Risk Index dataset API or downloadable datasets but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Federal Emergency Management Agency (FEMA), OpenFEMA Dataset: Disaster Declarations Summaries - v2, retrieved from https://www.fema.gov/api/open/v2/DisasterDeclarationsSummaries on November 2, 2026, 1:21 PM EST. This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).
Tornado records: NOAA/NWS Storm Prediction Center, Severe Weather Database, tornadoes 1950–2025 (https://www.spc.noaa.gov/wcm/data/1950-2025_actual_tornadoes.csv, downloaded 2 November 2026). Public domain; not endorsed by NOAA. Compiled by Global Incident Tracker.
Questions about DeKalb County
What natural disasters is DeKalb County, Illinois most at risk from?
DeKalb County, Illinois has a Relatively Low natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 80.8 out of 100, higher than about 80% of US counties, with cold waves, tornadoes and inland (river and flash) flooding scoring highest of its 18 hazards and $47 million a year in expected losses.
How many federal disaster declarations has DeKalb County had?
OpenFEMA lists 10 federal disaster declarations that included DeKalb County since 1973, not counting 2 for COVID-19; the latest is DR-4116-IL (Severe Storms, Straight-Line Winds, and Flooding, declared 10 May 2013). Another 2 Illinois declarations were made statewide without a county list.
How many tornadoes have hit DeKalb County?
NOAA's Storm Prediction Center recorded 30 tornadoes touching DeKalb County from 1950 to 2025. The deadliest: 9 Apr 2015, EF4, 30.1 mi path, 2 killed, 11 injured (deaths and injuries are for the whole path).
Is the National Risk Index a flood zone map?
No. The National Risk Index is a planning-level estimate for a whole county, built for nationwide comparison. It does not tell you the flood zone or the risk of a single property: for that, look up the address on FEMA's Flood Map Service Center (msc.fema.gov) and ask your local floodplain manager.