Pennsylvania
From the Johnstown Flood of 1889 to Hurricane Agnes in 1972 to Tropical Storm Ida in 2021, Pennsylvania's most costly and deadly hazard has always been water. The Susquehanna, Delaware, and Ohio rivers define the state, and they flood.
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Know your region
Harrisburg, Wilkes-Barre, Scranton, Williamsport. Hurricane Agnes (1972) devastated this entire corridor. Tropical Storm Lee (2011) put the river at near-record levels again. The Susquehanna is the longest river on the East Coast, and its flood history is relentless.
Primary hazards: flooding, winter storms, severe storms, tropical remnants
Philadelphia, Allentown, Reading, the Lehigh Valley. Tropical Storm Ida (2021) caused catastrophic flash flooding. Schuylkill River flooding threatens the metro. The Delaware River floods after heavy rain. Nor'easters bring heavy snow.
Primary hazards: flash flooding, hurricanes, severe storms, winter storms
Pittsburgh, Erie, Johnstown, the Allegheny Plateau. The confluence of the Allegheny, Monongahela, and Ohio rivers at Pittsburgh creates massive flood potential. Lake-effect snow buries Erie. The hilly terrain produces landslides during heavy rain. Mine subsidence is an additional risk in coal country.
Primary hazards: flooding, lake-effect snow, landslides, severe storms
Your hazard profile
Each links to a full guide with during-event protocol, recovery steps, and resources specific to PA.
Flooding is Pennsylvania's most frequent and costly hazard. Ida (2021) caused catastrophic flash flooding. The Johnstown Flood (1889) killed 2,209. The Susquehanna, Delaware, and Ohio rivers flood regularly. Many flood deaths occur in vehicles.
Read the flooding guide →
Northwestern PA receives heavy lake-effect snow from Lake Erie. Nor'easters bury the Poconos. Ice storms in central PA cause widespread outages. The 2010 Snowmageddon paralyzed the state.
Read the winter storms guide →
Severe storms with straight-line winds, hail, and tornadoes strike spring through fall. Pennsylvania averages 16 tornadoes per year. Microbursts in forested areas cause extensive tree damage and outages.
Read the severe thunderstorms guide →
Agnes (1972) caused catastrophic flooding across the state. Ida (2021) proved the risk persists. While direct hurricane impacts are rare, tropical remnants bring devastating rain and flooding.
Read the tropical remnants guide →
Pennsylvania's Appalachian terrain is prone to landslides during heavy rain. Pittsburgh's steep slopes and roadcuts are vulnerable. Mine subsidence in coal country is an additional risk.
Read the landslides guide →
Pennsylvania resources
Pennsylvania Emergency Management Agency. Coordinates disaster response and administers FEMA programs for the state.
Central Pennsylvania forecasts. Flood alerts, winter storm warnings, and severe weather for the Susquehanna corridor.
Southeast Pennsylvania forecasts. Flash flood warnings, tropical remnant tracking, and winter storm alerts for the Philadelphia metro.
Statewide referral service. Disaster recovery, energy assistance (LIHEAP), food banks, and housing resources.
The water keeps coming
The Johnstown Flood of 1889 killed 2,209 people. Hurricane Agnes in 1972 devastated the Susquehanna Valley. Tropical Storm Ida in 2021 caused catastrophic flash flooding in the Philadelphia suburbs. Pennsylvania's relationship with flooding is not occasional. It is foundational.
The state's topography creates the problem: steep Appalachian slopes funnel water into narrow valleys. The three major river systems, the Susquehanna, Delaware, and Ohio, all flood. Urban areas with aging storm sewers flood during heavy rain. Post-Agnes flood control infrastructure helps but cannot eliminate the risk.
For every Pennsylvania household, the flood question is not if but where and when. Know your flood zone. Carry flood insurance. Never drive through standing water. The state that experienced the Johnstown Flood is still the state most likely to flood again.