Today's Mosquito Risk in Pennsylvania: Real-Time Forecast & Activity Map
Check your ZIP code for local mosquito activity, West Nile risk, and prevention insights.
Built from CDC and NOAA data
Mosquito Surveillance Insights
- Annual WNV Cases
- about 80 to 150 confirmed cases annually
- Based on CDC ArboNET surveillance data
- Risk Tier
- Tier 3: Moderate
- Major urban Culex pressure plus warming Allegheny Plateau lifting case totals each year.
- Per mosquito-risk-model regional tier
- Highest-Risk Areas
- Philadelphia, Allegheny, Montgomery, Delaware, Bucks (WNV)
Current Situation in Pennsylvania
Pennsylvania carries the heaviest absolute WNV burden in the Mid-Atlantic, with roughly 80 to 150 confirmed human cases annually driven by the Philadelphia and Pittsburgh metros. Cx. pipiens populations in city storm drains and rowhouse basement sumps sustain transmission from June through frost. Aedes albopictus is established across the southern half of the state and pushing north each year. The Allegheny and Pocono mountain regions produce big floodwater Aedes hatches off forested wetlands and beaver ponds, while the Susquehanna and Delaware River bottomlands hold steady summer populations. EEE is rare. Biting season runs late May through early October, with peak risk in August.
Snapshot of the current mosquito situation in Pennsylvania, drawn from CDC ArboNET surveillance and the regional risk model.
- Risk Level
- Moderate
- Peak Activity
- May through September
- Dominant Vector
- Northern House Mosquito (Culex pipiens)
Where Mosquitoes Breed in Pennsylvania
Pennsylvania mosquito habitat splits between dense urban Culex grids and forested mountain wetlands. Philadelphia rowhouse alleys, Schuylkill River corridor catch basins, and Tinicum National Wildlife Refuge sustain the southeastern WNV load. Pittsburgh's three-rivers floodplains and the Allegheny industrial corridor drive the western metro Culex pressure. The Pocono Mountains hold cedar swamps and beaver-pond Aedes hatches across Monroe and Pike counties. The Allegheny Plateau forested wetlands produce dense forest mosquitoes through July. The Susquehanna River bottomlands across the central counties and the Lake Erie shoreline at Presque Isle round out the habitat mix.
Hotspot Counties & Areas
- Philadelphia County (urban Culex, Tinicum NWR, Fairmount Park)
- Allegheny County (Pittsburgh metro, three-rivers floodplain)
- Lehigh County (Allentown, Lehigh River corridor)
- Erie County (Lake Erie shoreline, Presque Isle)
- Monroe County (Pocono Mountains swamps)
- Lancaster County (Susquehanna River bottomlands)
- Bucks County (Delaware River corridor, suburban albopictus)
- Dauphin County (Harrisburg, central Susquehanna)
Seasonal Activity Pattern
Biting starts in late May in the Philadelphia and Pittsburgh metros, peaks late July through August, and tapers through September. WNV cases concentrate in August across the Philadelphia, Pittsburgh, and Allentown metros. Aedes albopictus daytime biting in southern suburbs runs from July through early October. The Allegheny and Pocono mountains run roughly two weeks behind the metros, with peak forest biting in mid to late July. Heavy summer storms produce floodwater Aedes pulses along the Susquehanna and Delaware bottoms.
Monthly Biting Intensity (Mid-Atlantic)
Pennsylvania Mosquito Risk Profile
- WNV burden level
- Moderate
- about 80 to 150 confirmed cases annually
- EEE risk
- Rare
- Peak biting season
- late May through early October
- Top urban risk areas
- Philadelphia (Philadelphia)
- Pittsburgh (Allegheny)
- Allentown (Lehigh)
- Erie (Erie)
Signature habitat: Philadelphia and Pittsburgh storm drains, Allegheny forested wetlands, Pocono swamps, Susquehanna floodplain.
Climate driver: Major urban Culex pressure plus warming Allegheny Plateau lifting case totals each year.
Check Your Local Mosquito Risk
Ready to see current mosquito activity in your area? Get today's forecast and personalized risk assessment for your ZIP code.
Common Mosquitoes in Pennsylvania
Understanding which mosquitoes are active in Pennsylvania helps you identify threats and take appropriate precautions. Click any card for details.
Asian Tiger Mosquito
Aedes albopictus
Risk: Eastern Equine Encephalitis, dengue, chikungunya, Zika, dog heartworm.
Key feature: A single bright white stripe down the center of the back.
Active: Spring through first hard frost. Eggs overwinter in cold climates and hatch when flooded by spring rain.
Northern House Mosquito
Culex pipiens
Risk: West Nile virus, St. Louis encephalitis, dog heartworm.
Key feature: Medium brown body with banded abdomen. Looks nearly identical to Cx. quinquefasciatus.
Active: Late spring through early fall in the north. Adult females overwinter in basements, garages, and storm drains.
Eastern Equine Encephalitis
Vector: Asian Tiger Mosquito
Eastern Equine Encephalitis
Rare but devastating, with roughly 30% case fatality. Concentrated in Northeast swamp areas and the Gulf Coast.
What to watch for
- Onset typically 2 to 15 days after a bite
- Most cases mild or asymptomatic, small fraction severe
- Neurological signs (severe headache, neck stiffness, confusion) need ER care
Breaking the Cycle in Pennsylvania
The mosquito lifecycle takes about a week. These habits cut local biting pressure faster than anything else, building multiple layers of protection.
Drain the Yard Weekly
Empty buckets, planter saucers, kiddie pools, tarps, and clogged gutters. A week of standing water is one full mosquito generation.
Repel Before Going Out
EPA-registered DEET (20-30%), picaridin (20%), IR3535, or oil of lemon eucalyptus. Apply before going outside, especially at dusk and dawn.
Seal the House
Window and door screens with no tears. AC and porch fans both work. Mosquitoes struggle to fly upwind even at 1-2 mph air speed.
Treat Outdoor Clothing
Permethrin-treated long sleeves and pants for evening yard work, hiking, or fishing. Remains effective through 70+ wash cycles.
If You Develop Symptoms
Most mosquito bites are harmless. A small fraction can transmit illness, and knowing the timeline matters more than panicking at every itch.Five things to know.
Watch for fever
Fever, body aches, headache, or fatigue 2 to 15 days after a bite. West Nile often feels like flu, and most infections never get diagnosed.
Note where and when
A rough record of where and when you got bitten helps your doctor decide what to test for. Date, location, mosquito-heavy areas you visited.
Get help fast for neuro signs
Severe headache, neck stiffness, confusion, vision changes, or sudden muscle weakness can mean neuroinvasive WNV or EEE. Both are medical emergencies.
Pregnant exposure?
If pregnant and bitten in an area with documented Zika or local dengue transmission, mention to your OB. Same goes for travel exposure.
Children and seniors
Higher risk of severe disease from WNV, EEE, and dengue in adults over 60 and children under 5. Early call to the pediatrician or PCP if symptoms appear.
When does mosquito season end in Pennsylvania?
Mosquito activity winds down after the first hard freeze, which in Pennsylvania typically arrives around Oct 10. See the local first-frost window and city-by-city freeze dates.
Pennsylvania first frost datesAlso worried about ticks in Pennsylvania?
Lyme disease risk and tick activity track different seasonal patterns than mosquitoes. See your Pennsylvania tick forecast.
View Pennsylvania tick forecastStay Safe in Pennsylvania
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