Is it allergy season in New Hampshire?

New Hampshire's allergy season is defined by its Appalachian forest character. The state's extensive birch and maple forests produce some of New England's highest spring pollen counts, compressed into a 6–8 week window by the short growing season. Manchester and Nashua in the south see the earliest onset — influenced by Massachusetts patterns. The White Mountains create a dramatic north-south gradient, with the North Country near Berlin seeing spring pollen 3–4 weeks later than the Seacoast. Ragweed is present in southern New Hampshire but shorter and milder than the Mid-Atlantic states to the south.

New Hampshire's north-south length creates meaningful variation. Manchester and Nashua in the south share a profile almost identical to northern Massachusetts — the state border means little botanically. The seacoast around Dover sees coastal moderation. Central NH around Concord and Keene has the full Appalachian forest season. The North Country above the White Mountains experiences the latest start and shortest season in the state.

Manchester / Nashua

Southern NH — earliest onset, Massachusetts influence

Manchester and Nashua are effectively extensions of the Massachusetts allergy zone. Maple and alder begin in March; birch peaks in late April; oak follows into May. These cities see the state's earliest pollen and highest urban concentrations. Ragweed season, while shorter than Boston's, is still meaningful in August–September.

Birch/Maple · Apr–MayOak · Apr–MayRagweed · Aug–Sep

Concord / Merrimack Valley

State capital and Appalachian river corridor

Concord sits in the Merrimack River valley surrounded by mixed hardwood and birch forest. The valley corridor can concentrate pollen on still mornings. Spring tree season is intense with birch and maple overlapping. The state capital's position in central NH means the full range of NH allergens.

Birch/Maple · Apr–MayGrass · Jun–JulRagweed · Aug–Sep

Seacoast / Dover-Portsmouth

Atlantic breezes provide partial afternoon relief

The Seacoast region benefits from Atlantic sea breezes that moderate afternoon pollen counts. However, morning hours before onshore flow develops can still see significant counts. The seacoast season is roughly 1–2 weeks shorter at either end than inland areas. Ragweed is milder here than in the Merrimack Valley.

Trees · Apr–May (moderated)Grass · Jun–JulRagweed milder · Aug–Sep

White Mountains / North Country

Elevation delays spring by 3–4 weeks

The White Mountains and North Country above Franconia Notch represent the most dramatic climate shift in the state. At elevations above 1,500 feet, spring tree pollen can arrive 3–4 weeks later than Manchester. The season is compressed and intense — birch at high elevation peaks harder but shorter. Ragweed is minimal north of the notches.

Birch delayed · May–JunShorter season overallRagweed minimal

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.

Birch pollen

Stone fruits, apples, nuts & vegetables

Apples, peaches, cherries, plums, pears, almonds, hazelnuts, walnuts, carrots, celery, parsley, kiwi

Peak risk April–May in New Hampshire. Birch has the broadest cross-reactivity of any common pollen — reacting with a wide range of fruits, tree nuts, and vegetables. New Hampshire's extensive birch forest makes this the state's most clinically significant OAS. Peeling fruit removes most of the cross-reactive protein concentrated in the skin.

Grass pollen

Tomatoes, potatoes & melons

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

Peak risk June–July. New Hampshire's grass season is shorter than southern states but still significant. Timothy, orchard grass, and Kentucky bluegrass are the dominant grasses in NH's fields and lawns.

Ragweed

Melons & bananas

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

Peak risk August–September. New Hampshire's ragweed season is shorter and milder than the Mid-Atlantic, but still meaningful in southern NH. The North Country above the White Mountains has minimal ragweed.

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.