NH · Allergy Season Guide
New Hampshire Allergy Season Guide
New Hampshire experiences a humid continental climate with four distinct seasons — cold, snowy winters and warm, humid summers.
Summary
New Hampshire has 0 active PollyMap collection sites, and is seeking partners in 5 additional cities. Tree pollen typically dominates early spring, grass pollen peaks in late spring and early summer, and weed pollen (including ragweed) extends from late summer through fall.
PollyMap collection status across New Hampshire
Statewide allergy overview
New Hampshire experiences a humid continental climate with four distinct seasons — cold, snowy winters and warm, humid summers.
Birch, oak, maple, and beech produce an intense April-May tree season. Grass pollen peaks in June, and ragweed lasts from mid-August through October.
Humid summers, dense tree cover, and heavy leaf decay drive elevated Alternaria and Cladosporium counts from late summer into fall.
Allergy patterns vary by elevation and proximity to coast or mountains within New Hampshire, but most of the state shares a common seasonal rhythm of spring tree pollen, summer grass pollen, and late-summer to fall weed pollen.
New Hampshire allergy calendar
Month-by-month intensity for the four major airborne allergen categories.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tree | Low | Mod | High | V.High | V.High | High | Mod | Low | Low | Low | Low | Low |
| Grass | — | — | Low | Mod | V.High | V.High | High | Mod | Low | Low | — | — |
| Weed | Low | Low | Low | Mod | Mod | Mod | High | V.High | V.High | High | Mod | Low |
| Mold | Low | Low | Mod | Mod | High | High | High | V.High | V.High | V.High | Mod | Low |
Top weed pollens
Top airborne molds
Major city guides in New Hampshire
Latest PollyMap reports for New Hampshire
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