Allegheny County, Pennsylvania Natural Disaster Risk
FEMA National Risk Index assessment · PA
HighComposite Risk Score
National percentile: 98th
Allegheny County faces high composite natural disaster risk (NRI Risk Index score 98.1, 98th national percentile), driven primarily by riverine flood and cold wave exposure. Expected annual loss across all 18 hazard types is $354M.
Source: FEMA National Risk Index v1.20 · Updated December 2025
Risk Overview
Allegheny County carries a high composite natural disaster risk, with a National Risk Index score of 98.1 out of 100 — placing it in the 98th national percentile and in the upper tier of natural-disaster risk nationally. The score blends Expected Annual Loss, Social Vulnerability, and Community Resilience across all 18 FEMA hazard types.
Risk here concentrates in riverine flood (rivers and streams overflowing their banks after heavy rain or snowmelt) at Very High risk — $295M in expected annual loss and about 7.32 events per year; cold wave (prolonged spells of dangerously low temperatures) at Very High risk — $32M in expected annual loss and about 2.84 events per year; and strong wind (damaging straight-line winds outside of tornadoes and hurricanes) at High risk — $4M in expected annual loss and about 2.35 events per year. Across all hazards, FEMA estimates $354M in expected annual loss for a population of 1.25M.
Beyond physical exposure, Allegheny County has a low social vulnerability rating (how susceptible the population is to harm) and a very high community resilience rating (its capacity to prepare for and recover from disasters). A less vulnerable population paired with strong resilience helps the community absorb and recover from events.
The county's disaster history tells the same story: Allegheny County has received 18 federal disaster declarations since 1972, including 5 for flood events and 4 for severe storm events. The most recent was Covid-19 Pandemic (biological), declared in March 2020.
Among 67 Pennsylvania counties, Allegheny County ranks #2 for overall natural disaster risk.
Top Hazards
All 18 Hazard Risks
| Riverine Flood | Very High | 7.32 / yr | $295M |
| Cold Wave | Very High | 2.84 / yr | $32M |
| Strong Wind | High | 2.35 / yr | $4M |
| Ice Storm | Very High | 0.40 / yr | $2M |
| Heat Wave | Medium | 1.95 / yr | $5M |
| Lightning | High | 42.59 / yr | $2M |
| Winter Weather | High | 11.21 / yr | $586K |
| Tornado | High | 0.28 / yr | $8M |
| Earthquake | Low | 0.00 / yr | $4M |
| Landslide | Low | 1.50 / yr | $42K |
| Hurricane | Low | 0.03 / yr | $1M |
| Wildfire | Very Low | 0.00 / yr | $91K |
| Hail | Very Low | 3.21 / yr | $135K |
| Avalanche | Very Low | 0.01 / yr | $94 |
| Coastal Flood | Very Low | 0.00 / yr | $0 |
| Drought | Very Low | 0.01 / yr | $0 |
| Tsunami | Very Low | 0.00 / yr | $0 |
| Volcanic Activity | Very Low | 0.00 / yr | $0 |
Disaster History
Allegheny County has received 18 federal disaster declarations since 1972, most recently Covid-19 Pandemic in March 2020. Most frequent causes: Flood (5), Severe Storm (4), Hurricane (3).
| Declared | Type | Disaster |
|---|---|---|
| March 2020 | Biological | Covid-19 Pandemic |
| March 2020 | Biological | Covid-19 |
| October 2013 | Severe Storm | Severe Storms, Tornadoes, and Flooding |
| October 2012 | Hurricane | Hurricane Sandy |
| April 2010 | Snowstorm | Severe Winter Storms and Snowstorms |
| September 2005 | Hurricane | Hurricane Katrina |
| September 2004 | Hurricane | Tropical Depression Ivan |
| September 2004 | Severe Storm | Severe Storms and Flooding Associated with Tropical Depression Frances |
| June 1998 | Severe Storm | Severe Storms, Tornadoes,and Flooding |
| January 1996 | Flood | Severe Storms and Flooding |
Showing the 10 most recent of 18 declarations.
Source: FEMA Disaster Declarations Summaries (OpenFEMA).
Frequently Asked Questions
What is the overall natural disaster risk for Allegheny County?
Allegheny County has a composite FEMA National Risk Index score of 98.1 out of 100, placing it in the High category and the 98th national percentile. This combines Expected Annual Loss, Social Vulnerability, and Community Resilience across 18 hazard types.
What are the top natural hazards in Allegheny County?
The three highest-rated hazards are Riverine Flood (Very High, $295M EAL), Cold Wave (Very High, $32M EAL), Strong Wind (High, $4M EAL). These account for most of the county's expected annual losses.
How does Allegheny County compare to other Pennsylvania counties?
Allegheny County ranks #2 of 67 Pennsylvania counties for overall natural disaster risk, with a high rating.
How many federally declared disasters has Allegheny County had?
FEMA records 18 federal disaster declarations for Allegheny County since 1972, most often 5 for flood events and 4 for severe storm events. The most recent was Covid-19 Pandemic, declared in March 2020.
What does Expected Annual Loss (EAL) mean?
EAL is FEMA's estimate of average annual dollar losses from natural hazards, calculated from historical event data and exposure models. Allegheny County's $354M EAL is a statistical average, not a guarantee for any specific year or address.