Portsmouth pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Portsmouth is moderate; ragweed is moderate; grass is low.
Pollen Tomorrow
Tomorrow (21 September 2026) grass increasing, ragweed increasing, mugwort at low levels.
7-Day Trend
Over the next week grass, mugwort, and ragweed will decrease.
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Pollen Risk
Today - 20 September
| Pollen species | Level | Value |
|---|---|---|
| Alder (Alnus) | None | 0/100 |
| Birch (Betula) | None | 0/100 |
| Hazel (Corylus) | None | 0/100 |
| Cypress (Cupressaceae) | None | 0/100 |
| Grass (Poaceae) | Low | 12/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | None | 0/100 |
| Ragweed (Ambrosia) | Moderate | 34/100 |
Tomorrow - 21 September
| Pollen species | Level | Value | 7-Day Trend |
|---|---|---|---|
| Alder (Alnus) | None | 0/100 | — |
| Birch (Betula) | None | 0/100 | — |
| Hazel (Corylus) | None | 0/100 | — |
| Cypress (Cupressaceae) | None | 0/100 | — |
| Grass (Poaceae) | Moderate | 33/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | Low | 21/100 | |
| Ragweed (Ambrosia) | High | 55/100 |
Local Environmental Conditions
Portsmouth's parks in New Hampshire and the Piscataqua River corridor feature oak, birch, and maple as the main tree pollen sources, with exposure varying between these green areas and the more built-up city centre. Surrounding New Hampshire Seacoast woodland and farmland contribute substantial tree and grass pollen, while the coastal position means onshore Atlantic winds can periodically disperse urban pollen.
Portsmouth's pollen season in Virginia opens with oak and pine from late January, followed by sweet gum through February and March. Grass pollen peaks through May and June, with ragweed extending the season into October. The Hampton Roads waterways and Chesapeake Bay position mean coastal breezes can periodically disperse pollen, while surrounding Virginia coastal plain woodland contributes substantial tree and grass pollen throughout the extended season.
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Pollen forecast neighborhoods 1 neighborhood
Frequently Asked Questions About Pollen in New Hampshire
Is pollen high in Portsmouth right now?
On 20 September 2026, overall pollen levels in Portsmouth are moderate. Ambrosia is the main contributor to airborne pollen, while grass remain at lower levels
Will pollen levels change in Portsmouth tomorrow?
On 21 September 2026, pollen conditions in Portsmouth will be different from today, with artemisia at low levels and ambrosia, grass increasing
Is pollen expected to decrease in Portsmouth this week?
According to the five-day outlook, ambrosia, artemisia, and grass pollen levels are expected to gradually decrease, suggesting improving conditions later in the week.
Which pollen types are currently active in Portsmouth?
On 20 September 2026, Ambrosia is the dominant pollen source in Portsmouth. grass are also present but at lower levels. artemisia are not currently active.
When is pollen season in Portsmouth?
How often is the Portsmouth pollen forecast updated?
The Portsmouth pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Portsmouth come from nearby or far away?
Studies show that most pollen exposure (often 70–90%) comes from nearby sources, such as local trees and vegetation. A good pollen forecast therefore depends on accurately representing local vegetation. Pollen can travel long distances, but this usually matters only early in the season or during specific wind events.
Are pollen levels in Portsmouth based on measurements or forecasts?
Pollen data is often misunderstood. Most "pollen levels" are not real-time measurements, but forecasts.
Direct pollen measurements are typically delayed by 1-2 days because they require manual analysis. To show current conditions in Portsmouth, modern forecasts combine recent measurements, weather data, and information about local vegetation.
This allows us to estimate pollen levels for today and the coming days, not just report the past.
Airmine’s atmospheric monitoring platform was developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team, using satellite and Earth observation technologies to improve emissions monitoring.
Understanding the Scale
The 0–100 scores represent risk levels, not direct measurements of pollen or air pollutant concentrations. Higher scores indicate higher risk. Pollen and air quality use different thresholds.
Pollen
| None | 0 | No or negligible risk of exposure. Pollen/mold exposure is expected to be minimal. |
| Low | 0-25 | Low risk of exposure. Small amounts of pollen or mold spores may be present. |
| Moderate | 25-50 | Moderate risk of exposure. Pollen/mold exposure is expected to be noticeable. |
| High | 50-75 | High risk of exposure. Elevated pollen/mold exposure is expected. |
| Very High | 75-100 | Very high risk of exposure. Pollen/mold exposure is expected to be at or near its highest levels. |
Get More in the Airmine Pollen app
Get 15-day pollen forecasts with morning, afternoon and evening detail, plus 5-day air quality forecasts. Explore interactive pollen risk maps, estimated pollen season start, route profiles and a symptoms diary.
Features and forecast availability vary by region. Currently covering Europe, the contiguous US, southern Canada, South Africa, Australia, Indonesia (Java & Bali), Brazil, Paraguay, Uruguay and the Buenos Aires area.
Developed with support from the European Space Agency (ESA) Business Applications and Space Solutions (BASS).
