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Real-time pollen data for Harrisburg — updated daily.
Harrisburg is surrounded by some of the most densely forested terrain in the eastern United States, and the Susquehanna River Valley concentrates tree pollen from the surrounding Appalachian ridges. Oak is the dominant tree allergen in central Pennsylvania, producing heavy, sustained pollen loads from April through May. Hickory trees are common throughout the region and produce particularly potent allergenic pollen. Maple and box elder begin pollinating early, often by March, as one of the first signs of spring in the valley. Cedar pollen appears in late winter and early spring. Mulberry trees contribute significant allergenic pollen in spring. Willow trees along the Susquehanna River and its tributaries release pollen in March and April. Ash trees contribute to the spring pollen mix, though emerald ash borer has reduced ash populations in recent years. Birch, walnut, elm, and cottonwood round out the diverse spring tree pollen profile. The ridge-and-valley geography of central Pennsylvania means that pollen released from forested slopes funnels down into the Susquehanna Valley floor where Harrisburg sits, concentrating tree pollen exposure in the populated lowland areas.
Grass pollen season in Harrisburg runs from approximately mid-May through mid-August, overlapping with the tail end of tree pollen in late May and the beginning of weed pollen in late July. Timothy grass is the most significant grass allergen in the region, found in fields, roadsides, and pastures throughout the Susquehanna Valley. Ryegrass is a common allergen in residential lawns and open areas. Bent grass, brome grass, and orchard grass contribute to the grass pollen burden. Fescue is present in both residential landscapes and agricultural settings. Bermuda grass appears during the warmest months. The agricultural land surrounding Harrisburg — particularly the productive farmland of Lancaster, Cumberland, and Dauphin counties — creates extensive grass and crop pollen sources that add to the residential lawn and park exposure within the city.
Ragweed is the dominant fall allergen in the Harrisburg area and across central Pennsylvania. Ragweed season typically begins in mid-August and continues until the first hard frost, which arrives by late October to early November. Ragweed pollen is lightweight and travels long distances on wind, making it essentially unavoidable during peak season regardless of proximity to ragweed plants. Wormwood is another significant fall allergen in the central Pennsylvania region. Pigweed and amaranth contribute additional weed pollen. Sagebrush pollen is present in fall, though at lower levels than in western states. Dock and lamb's quarters add to the weed pollen mix. The agricultural landscape surrounding Harrisburg provides abundant disturbed soils, field edges, and open land where ragweed and other weeds thrive.
Central Pennsylvania's humid summers create ideal conditions for outdoor mold growth, with Alternaria and Cladosporium as the most common species. Mold spore counts peak during warm, humid months and surge again during fall leaf decomposition. The Susquehanna River and its floodplain contribute moisture to the local environment, supporting mold growth in riverside areas and neighborhoods prone to periodic flooding. Indoor mold is common in basements — standard in Harrisburg-area homes — particularly in older housing stock where moisture management is inadequate. Dust mites thrive in the humid climate, particularly during summer months. Pet dander is a significant year-round indoor allergen. Winter drives residents indoors for four to five months, concentrating exposure to dust mites, mold, and pet dander in sealed, heated homes.
Severity: Low (Outdoor) / Moderate (Indoor)
Harrisburg winters bring cold temperatures with average January highs near 37°F. Snow cover is intermittent, and outdoor pollen is largely absent from December through early March. Homes sealed against the cold concentrate indoor allergens — forced-air heating circulates dust mites, pet dander, and mold spores. Basements in Harrisburg's older housing stock are prone to dampness and mold. By late March, the earliest trees — elm, maple, and cedar — begin pollinating, often before residents expect spring allergies to start. This is the best time to start preventive allergy medications before the spring surge arrives.
Severity: High to Severe
April and May are Harrisburg's most intense allergy months. Oak, hickory, maple, mulberry, cedar, ash, willow, birch, and walnut release pollen in overlapping waves that saturate the Susquehanna Valley. The surrounding Appalachian ridges funnel pollen downslope into the valley floor, concentrating exposure in populated areas. April is typically the single worst month for tree pollen. By late May, grass pollen begins overlapping with late tree pollen, creating a transition period with multiple allergen types airborne simultaneously. Warm, windy spring days scatter pollen across the valley with no geographic barriers within the lowland to limit dispersal.
Severity: Moderate to High
Timothy grass, ryegrass, brome, orchard grass, and fescue peak from late May through July. Central Pennsylvania's humid summers create ideal conditions for outdoor mold growth, and mold spore counts rise significantly during this period. Summer thunderstorms temporarily wash pollen from the air but spike mold spore counts as moisture activates dormant colonies. By August, ragweed pollen begins appearing, overlapping with the tail end of grass season and elevated mold. The combination of grass pollen, emerging weed pollen, and high mold creates a multi-allergen burden during the hottest weeks of summer. Air quality can occasionally deteriorate during summer heat waves, with ozone and fine particulate matter adding respiratory stress.
Severity: Moderate to High
Ragweed pollen dominates from September through the first hard frost, typically arriving by late October. The agricultural landscape surrounding Harrisburg supports abundant ragweed in farm fields, along roads, and in disturbed areas. Wormwood and pigweed contribute additional weed pollen. Fall leaf decomposition creates a significant outdoor mold surge. The combination of ragweed pollen and elevated mold makes early fall a challenging dual-allergen period. Canadian wildfire smoke can affect Harrisburg's air quality during fall, as demonstrated by hazardous air quality events from smoke that traveled across the Northeast.
Severity: Low
The first hard freeze ends the outdoor pollen season. November and December provide genuine pollen relief for Harrisburg residents. The transition to sealed indoor environments begins the winter indoor allergen cycle. Forced-air heating stirs up dust and circulates indoor allergens. This is an excellent window for allergy testing, deep cleaning, and starting a treatment plan before the next spring.
Harrisburg sits on the Susquehanna River valley floor, flanked by Blue Mountain to the north and lower Appalachian ridges to the south and east. This ridge-and-valley geography creates a natural pollen trap: during spring, tree pollen released from forested slopes funnels down into the valley where it concentrates at lower elevations. On calm days, pollen can linger in the valley air longer than it would in flat, open terrain where winds disperse it. This geographic concentration effect means Harrisburg residents often experience higher effective pollen exposure than people living on the ridges above, even though they may have fewer trees in their immediate neighborhoods.
Tree pollen in the Susquehanna Valley peaks in April when oak, hickory, maple, mulberry, and other species release simultaneously. By the time you notice symptoms, the inflammatory cascade in your airways is already well established and harder to control. Starting antihistamines and nasal corticosteroids in mid-March — before symptoms appear — is significantly more effective than beginning after you're already miserable. Getting ahead of the inflammation is one of the most impactful things Harrisburg allergy sufferers can do each year.
Harrisburg sits in the heart of some of Pennsylvania's most productive agricultural land. The farmland of Cumberland, Dauphin, Lancaster, and Lebanon counties surrounds the metro area, and agricultural activity creates abundant disturbed soils and field edges where ragweed thrives. If your worst allergy period runs August through October, ragweed is almost certainly your primary trigger. The agricultural landscape also contributes dust and mold during harvest season, adding to the fall allergen burden beyond ragweed alone.
Most homes in the Harrisburg area have basements, and central Pennsylvania's humid climate combined with older housing stock makes basement moisture a chronic issue. Mold growing in damp basements, crawl spaces, and around foundation walls is one of the most common hidden allergen sources in the region. If your allergy symptoms persist year-round — including during the pollen-free winter months — indoor mold is a likely contributor. Use a dehumidifier to keep basement humidity below 50 percent and address any water intrusion from the Susquehanna's periodic flooding or spring snowmelt.
While Harrisburg isn't traditionally associated with wildfire smoke, Canadian wildfire events have produced hazardous air quality in central Pennsylvania in recent years. During these events, Harrisburg experienced some of the worst air quality readings in the state, with authorities advising residents to stay indoors. Wildfire smoke contains fine particulate matter that inflames airways and dramatically worsens allergy and asthma symptoms. If you notice respiratory symptoms worsening during summer or fall smoke events, your treatment plan may need adjustment for these increasingly common episodes.
HeyAllergy offers telemedicine appointments with board-certified allergists and immunologists licensed in Pennsylvania. Book a virtual consultation from anywhere in central PA — Harrisburg, Hershey, Carlisle, Mechanicsburg, Camp Hill, or surrounding areas — without the wait for a local specialist opening. Have allergy blood tests ordered at a convenient local lab and receive your personalized treatment plan. HeyPak sublingual immunotherapy drops ship directly to your door and treat the root cause of allergies by building tolerance to your specific central Pennsylvania triggers.
April and May are typically Harrisburg's worst allergy months, when oak, hickory, maple, mulberry, and other trees release peak pollen loads into the Susquehanna Valley. September brings a second surge from ragweed and fall mold. The ridge-and-valley geography concentrates pollen in the valley floor where the city sits, intensifying exposure during both peak seasons.
The most common allergens in the Harrisburg area are oak pollen, ragweed, Timothy grass, hickory, maple, mold spores, and dust mites. Oak and ragweed are typically the two most impactful seasonal allergens. A blood allergy test identifies your specific triggers from the full range of central Pennsylvania allergens.
Harrisburg sits on the valley floor between Appalachian ridges. Tree pollen from surrounding forested slopes funnels into the valley and concentrates at lower elevations. On calm days, pollen lingers in the valley air rather than dispersing. The humid climate supports high mold levels, and surrounding agricultural land provides habitat for abundant ragweed. This combination of geography, vegetation, and humidity creates a particularly challenging allergy environment.
Yes. HeyAllergy provides telemedicine appointments with board-certified allergists and immunologists licensed in Pennsylvania. Book a virtual consultation from anywhere in the state, have allergy blood tests ordered at a lab near you, and start a personalized treatment plan without visiting a clinic. No referral needed and no waitlist.
HeyPak sublingual immunotherapy uses customized liquid drops placed under your tongue daily. The drops contain precise doses of the specific allergens triggering your symptoms — whether oak, ragweed, Timothy grass, hickory, mold, or dust mites. Over time, your immune system builds tolerance, reducing allergic reactions and medication dependence. Most patients notice improvement within 3 to 6 months.
HeyAllergy accepts Medicare and most major PPO health plans, including United Healthcare, Health Net, Anthem Blue Cross, Anthem Blue Cross Blue Shield, Blue Shield, Cigna, Aetna, Humana, Oscar, and Tricare. Contact your insurance provider with Tax ID: 85-0834175 to confirm your specific telemedicine coverage.
Harrisburg's cold winters provide genuine pollen relief from roughly November through early March. However, tree pollen surges in March through May, grass pollen runs May through August, ragweed extends from August through October, and mold is elevated from June through November. Indoor allergens — dust mites, pet dander, and basement mold — persist year-round, particularly during winter when homes are sealed.
HeyAllergy offers fast scheduling with no waitlist. Book a telemedicine appointment with a board-certified allergist and connect from home using your phone, tablet, or computer. Residents throughout central Pennsylvania can access specialist allergy care without waiting weeks for a local opening.
Harrisburg, the capital of Pennsylvania, sits along the Susquehanna River in the heart of the state's ridge-and-valley region. With a population of approximately 50,000 in the city proper — and roughly 580,000 in the broader Harrisburg-Carlisle metro area including Hershey, Mechanicsburg, and Camp Hill — the Capital Region occupies a distinctive geographic position for allergy sufferers. Blue Mountain rises to the north, lower Appalachian ridges extend to the south and east, and the wide Susquehanna River valley floor stretches between them. This topography creates a natural pollen concentration effect: tree pollen released from the densely forested slopes funnels downward into the valley where it lingers at lower elevations, particularly on calm days. For Harrisburg residents, this means the surrounding forested ridges — while beautiful — are a constant source of airborne allergens that concentrate in the populated areas where people live and work.
Harrisburg sits at the intersection of some of Pennsylvania's most productive agricultural counties. Cumberland County to the west, Lancaster County to the southeast, Dauphin County surrounding the city, and Lebanon County to the east all contain extensive farmland. This agricultural landscape does more than grow crops — it creates ideal conditions for ragweed and other weed allergens. Disturbed agricultural soils, field edges, roadsides, and fallow land provide abundant habitat for ragweed, which thrives in exactly these conditions. When ragweed season begins in mid-August, the sheer acreage of ragweed-friendly terrain surrounding Harrisburg means pollen levels are sustained and intense through the first frost. The agricultural cycle also contributes dust and mold during harvest season in fall, adding to the allergen burden beyond ragweed pollen alone. For residents whose worst allergy period falls in August through October, the agricultural landscape is a major contributing factor.
Central Pennsylvania's humid continental climate creates summer conditions that support robust mold growth both indoors and outdoors. The Susquehanna River and its tributaries — including the Yellow Breeches Creek and Conodoguinet Creek — create a moisture-rich environment along the valley floor. Outdoor mold spore counts peak during warm, humid months and surge again during fall leaf decomposition as moisture activates spore colonies on decaying organic matter. The river corridor itself supports vegetation and organic material that serves as mold substrate. Indoor mold is a significant concern in Harrisburg's housing stock, which includes many older homes with basements prone to chronic moisture issues. The city's proximity to the Susquehanna also means certain neighborhoods have experienced periodic flooding, creating conditions where basement and foundation moisture problems persist long after floodwaters recede. For residents whose symptoms persist year-round regardless of outdoor pollen levels, indoor mold and dust mites are nearly always contributing factors.
While central Pennsylvania isn't traditionally associated with wildfire smoke exposure, this has changed in recent years. Smoke from Canadian wildfires has produced hazardous air quality conditions in Harrisburg and across south-central Pennsylvania, with state officials advising residents to remain indoors. During these events, Harrisburg experienced some of the worst air quality readings in the Commonwealth. The fine particulate matter in wildfire smoke inflames airways and dramatically worsens respiratory symptoms in people with existing allergies and asthma. As climate change continues to intensify wildfire seasons across North America, these smoke events are becoming a more regular part of Harrisburg's respiratory health landscape rather than rare anomalies.
Harrisburg's humid continental climate supports a full four-season allergy calendar with minimal gaps between allergen types. Spring tree pollen surges from March through May, with April typically the worst month. Grass pollen overlaps beginning in late May and extends through August. Ragweed and fall weeds take over from mid-August through the first frost in late October. Mold spore counts are elevated from June through November. The brief transitions between seasons often feature overlapping allergen types — tree and grass pollen simultaneously in late May, grass and ragweed together in August, ragweed and mold through October. Winter provides genuine pollen relief from roughly November through February, but indoor allergens fill the gap. The practical result is that residents with multiple sensitivities can experience symptoms across nearly the entire year, with only a few weeks of genuine respite.
HeyAllergy's telemedicine platform connects central Pennsylvania residents to board-certified allergists and immunologists licensed in the state. A virtual consultation from your home in Harrisburg, Hershey, Carlisle, Mechanicsburg, Camp Hill, or anywhere in the surrounding area eliminates the wait for specialist availability. Allergy blood tests are ordered at a convenient local lab, and a personalized treatment plan is developed based on your specific triggers. HeyPak sublingual immunotherapy drops ship directly to your door and treat the root cause of allergies by building your immune system's tolerance to central Pennsylvania allergens — from oak and ragweed to Timothy grass and mold. For a valley environment where geography concentrates pollen and humidity fuels mold, identifying and treating the root cause offers relief that medications alone often cannot provide.
