Allegheny County, Pennsylvania: Natural Disaster Risk and History
Allegheny County, Pennsylvania has a Relatively High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 98.1 out of 100, higher than about 98% of US counties, with inland (river and flash) flooding, cold waves and strong winds scoring highest of its 18 hazards and $354 million a year in expected losses.
OpenFEMA lists 16 federal disaster declarations that included Allegheny County since 1972, not counting 2 for COVID-19; the latest is DR-4149-PA (Severe Storms, Tornadoes, and Flooding, declared 1 October 2013). NOAA's Storm Prediction Center recorded 28 tornadoes touching Allegheny County from 1950 to 2025.
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Population 1,249,907 Buildings worth $294 billion Area 752 sq mi Risk rank in Pennsylvania 2 of 67 FIPS 42003
All 18 hazards, highest risk first
FEMA National Risk Index| Hazard | Risk rating | Score | Expected loss a year | How often | Events in record |
|---|---|---|---|---|---|
| Inland flooding | Very High | 99.2 | $295 million | about 7.3 a year | 205 |
| Cold wave | Very High | 98.8 | $32 million | about 2.8 a year | 54 |
| Strong wind | Relatively High | 96.3 | $3.8 million | about 2.4 a year | 90 |
| Ice storm | Very High | 96.1 | $2.0 million | about once every 2.5 years | 27 |
| Heat wave | Relatively Moderate | 94.3 | $5.4 million | about 2 a year | 36 |
| Lightning | Relatively High | 93.7 | $1.7 million | about 43 a year | 1,120,817 strikes |
| Winter weather | Relatively High | 93.3 | $586,024 | about 11 a year | 213 |
| Tornado | Relatively High | 91.2 | $8.4 million | about once every 3.6 years | 16 |
| Earthquake | Relatively Low | 87.9 | $4.0 million | rarer than once in 1,000 years | — |
| Landslide | Relatively Low | 87.2 | $42,239 | about 1.5 a year | — |
| Hurricane | Relatively Low | 75.9 | $1.2 million | about once every 37 years | 10 |
| Wildfire | Very Low | 60.4 | $90,814 | rarer than once in 1,000 years | — |
| Hail | Very Low | 31.3 | $135,049 | about 3.2 a year | 122 |
| Avalanche | Very Low | 28.1 | $94 | about once every 100 years | 0 |
| Drought | No Rating | 0.0 | — | about once every 69 years | 14 |
| 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 16
Most common: Flood 5, Severe Storm 4, Hurricane 3, Snowstorm 3.
| Decade | Declarations | Incident types |
|---|---|---|
| 1970s | 1 | Flood |
| 1980s | 4 | Flood ×3, Tornado |
| 1990s | 5 | Severe Storm ×2, Snowstorm ×2, Flood |
| 2000s | 3 | Hurricane ×2, Severe Storm |
| 2010s | 3 | Severe Storm, Hurricane, Snowstorm |
The last 10
Widest declarations that included Allegheny County
- Hurricane Sandy (2012, EM-3356-PA): 67 Pennsylvania counties designated.
- Hurricane Katrina (2005, EM-3235-PA): 67 Pennsylvania counties designated.
- Tropical Depression Ivan (2004, DR-1557-PA): 67 Pennsylvania counties designated.
Named storms in its declarations: Hurricane Sandy (2012), Hurricane Katrina (2005), Tropical Depression Ivan (2004), Tropical Depression Frances (2004), Tropical Storm Agnes (1972).
Not counted above: 2 COVID-19 ("Biological") declarations — in 2020 every US county was included. Pennsylvania also had 5 statewide declarations with no county list.
Tornado record since 1950 28
| Tornadoes touching the county | 28 |
|---|---|
| Strongest-rated | (E)F4 ×1 |
| Peak month | June (10) |
| Deadliest | 3 Aug 1963, F3, 0.1 mi path, 2 killed, 70 injured |
| Longest path | 4 Jun 1975, F2, 45.3 mi path |
| Most recent | 20 Nov 2024, EF0, 1 mi path |
| Deaths / injuries on those paths | 2 / 275 |
| Rating | (E)F0 | (E)F1 | (E)F2 | (E)F3 | (E)F4 | (E)F5 | Unrated |
|---|---|---|---|---|---|---|---|
| Count | 12 | 10 | 3 | 1 | 1 | 0 | 1 |
| Decade | 1950s | 1960s | 1970s | 1980s | 1990s | 2000s | 2010s | 2020s |
|---|---|---|---|---|---|---|---|---|
| Count | 2 | 1 | 4 | 3 | 3 | 2 | 2 | 11 |
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 Allegheny County compares with its 5 nearest counties
| County | Distance | Overall risk | Score | Top hazard |
|---|---|---|---|---|
| Allegheny County (this page) | — | Relatively High | 98.1 | Inland flooding |
| Washington County | 38 km | Relatively Moderate | 83.1 | Landslide |
| Beaver County | 39 km | Relatively Low | 75.3 | Inland flooding |
| Westmoreland County | 47 km | Relatively Moderate | 87.8 | Lightning |
| Butler County | 50 km | Relatively Low | 79.3 | Lightning |
| Hancock County, WV | 50 km | Very Low | 40.7 | Landslide |
Nearest by distance between county centres. Every county in Pennsylvania, ranked.
Vulnerability and resilience
| Social vulnerability | Relatively Low 32.7 |
|---|---|
| Community resilience | Very High 91.9 |
| Community risk factor | 0.99 |
| Expected annual loss, all hazards | $354 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 Allegheny County's main hazards
- Right now: National Weather Service alerts for Pennsylvania · all official warnings on Global Incident Tracker.
- Inland flooding: Flood safety: why shallow water kills · Floods recorded
- Cold wave: Carbon monoxide in winter · Power outages now
- Strong wind: Power outages now
- 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 Allegheny County
What natural disasters is Allegheny County, Pennsylvania most at risk from?
Allegheny County, Pennsylvania has a Relatively High natural-hazard risk rating in FEMA's National Risk Index (v1.20, December 2025): a score of 98.1 out of 100, higher than about 98% of US counties, with inland (river and flash) flooding, cold waves and strong winds scoring highest of its 18 hazards and $354 million a year in expected losses.
How many federal disaster declarations has Allegheny County had?
OpenFEMA lists 16 federal disaster declarations that included Allegheny County since 1972, not counting 2 for COVID-19; the latest is DR-4149-PA (Severe Storms, Tornadoes, and Flooding, declared 1 October 2013). Another 5 Pennsylvania declarations were made statewide without a county list.
How many tornadoes have hit Allegheny County?
NOAA's Storm Prediction Center recorded 28 tornadoes touching Allegheny County from 1950 to 2025. The deadliest: 3 Aug 1963, F3, 0.1 mi path, 2 killed, 70 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.