Is it allergy season in Pennsylvania?

Pennsylvania's allergy calendar is shaped by its geography: the Delaware Valley lowlands on the east experience an early, intense spring, while the Appalachian ridges push pollen season 1–2 weeks later as elevation increases. Both Philadelphia and Pittsburgh rank in the AAFA's top challenging allergy cities. The state's extensive forested hillsides mean tree pollen — especially birch, oak, and maple — is intense, followed by a severe ragweed season in fall.

Pennsylvania's four major regions — Philadelphia Metro, Western PA (Pittsburgh), the Susquehanna Valley (Harrisburg), and the Pocono/Lehigh Valley — each have distinct allergy profiles shaped by elevation, proximity to forested ridges, and prevailing wind patterns.

Philadelphia Metro

Early, intense spring — Delaware Valley floor

The Philadelphia metro sits in the Delaware Valley lowland, where warmer temperatures and low elevation produce the state's earliest and most intense tree pollen season. March through May is brutal — birch and oak overlap with each other and with maple and elm. The Atlantic coastal influence keeps ragweed moderate by Midwest standards, but still severe by any other measure.

Trees · Mar–May (early) Birch / Oak overlap Ragweed · Aug–Sep

Western PA (Pittsburgh)

River valleys trap pollen — compressed season

Pittsburgh's famous three rivers create topographic traps where pollen concentrates on calm evenings. The Appalachian elevation delays spring about 1–2 weeks behind Philadelphia. Tree season April–May is severe given the extensive deciduous forest cover of western Pennsylvania. Pittsburgh ranks alongside Philadelphia as one of PA's hardest allergy cities.

Trees · Apr–May River valley trapping Ragweed · Aug–Sep

Susquehanna Valley

Harrisburg — statewide crossroads timing

The broad Susquehanna River valley runs through Harrisburg and provides a low-elevation corridor between the eastern and western mountain ridges. Pollen timing is roughly in between Philadelphia and Pittsburgh. Grass pollen is notable here — the valley floor supports significant agriculture. A reliable ragweed season follows in late summer.

Trees · Apr–May Grass · Jun–Jul Ragweed · Aug–Sep

Pocono / Lehigh Valley

Elevation delays and extends the season

The Poconos and Lehigh Valley experience a compressed but sometimes severe tree season — higher elevation means later bloom, but also that tree species overlap more than at lower elevations. Allentown and Bethlehem see heavy birch given the northern forest character. Ragweed is present but moderated by cool fall nights that arrive early at elevation.

Birch · Apr–May (intense) Grass · Jun–Jul Ragweed · Aug–Sep (shorter)

Each row shows a full year of pollen for one region — trees in blue, grasses in green, weeds in amber. Look for where all three rows go quiet at the same time — that's your window.

Oral Allergy Syndrome (also called pollen-food allergy syndrome) causes tingling or mild itching in the mouth when you eat certain raw foods during the relevant pollen season. The proteins in the food are similar enough to the pollen protein that your immune system cross-reacts. Cooking usually deactivates the offending protein, so the same food cooked may cause no reaction.

Oak & Birch pollen

Stone fruits & apples

Apples, peaches, cherries, plums, pears, almonds, hazelnuts, carrots, celery

Peak risk April–May in PA. Birch and oak are both significant across Pennsylvania's forested Appalachian belt — one of the highest-birch states in the country. Peeling fruit helps — most of the cross-reactive protein is in the skin.

Grass pollen

Tomatoes, potatoes & melons

Tomatoes, potatoes, kiwi, watermelon, cantaloupe, oranges (in some cases)

Peak risk June–July. Pennsylvania's agricultural valleys produce substantial grass pollen, especially around Harrisburg and the Susquehanna corridor.

Ragweed

Melons & bananas

Watermelon, cantaloupe, honeydew, banana, zucchini, cucumber, sunflower seeds

Peak risk August–September. Philadelphia and Pittsburgh are both in the high-ragweed belt — the Delaware Valley lowlands are particularly ragweed-heavy in late summer.

Not medical advice. If you suspect OAS, speak with an allergist — it can sometimes progress, and symptoms that extend beyond the mouth should be evaluated.