Washington pollen forecast — United States Capitol neighborhood
Pollen Today
Today (20 September) pollen in United States Capitol, Washington is high; ragweed is high; grass is moderate; mugwort is low.
Pollen Tomorrow
Tomorrow (21 September 2026) grass declining, ragweed declining, mugwort no longer expected.
7-Day Trend
Over the next week grass, mugwort, and ragweed will increase.
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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) | Moderate | 40/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Low | 4/100 |
| Ragweed (Ambrosia) | High | 63/100 |
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) | Low | 14/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | Moderate | 35/100 |
Local Environmental Conditions
United States Capitol is the Capitol grounds, a landscaped hilltop park designed by Frederick Law Olmsted at the Mall's eastern end. Vegetation here reflects the wider Washington area, with tree and grass pollen exposure following the same regional pattern as the rest of the city. As with most sublevel sites, local landscaping can shift counts slightly from the citywide average.
At United States Capitol, a landmark in Washington, the pollen season opens with cedar and elm from late February with oak following close behind through April. Grass follows, peaking through May and June, while ragweed and mugwort extend the weed season into September. The mild mid-Atlantic climate advances the season compared to more northern East Coast cities, a pattern felt across this part of Washington.
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Resource Hub
Pollen forecast neighborhoods 30 neighborhoods
Sports venues in Washington 1 sports venue
Frequently Asked Questions About Pollen in District of Columbia
Is pollen high in Washington right now?
On 20 September 2026, overall pollen levels in Washington are high. Ambrosia is the main contributor to airborne pollen, while grass and artemisia remain at lower levels
Will pollen levels change in Washington tomorrow?
On 21 September 2026, pollen conditions in Washington will be different from today, with ambrosia, grass continuing to decline
Is pollen expected to decrease in Washington this week?
According to the five-day outlook, ambrosia, artemisia, and grass pollen levels will increase later in the week.
Which pollen types are currently active in Washington?
On 20 September 2026, Ambrosia is the dominant pollen source in Washington. grass and artemisia are also present but at lower levels.
When is pollen season in Washington?
How often is the Washington pollen forecast updated?
The Washington pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Washington 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 Washington 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 Washington, 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).
