Foster City Pollen Forecast - Today, Tomorrow and the Week Ahead
Pollen Today
Today (6 October) pollen in Foster City is moderate; ragweed is moderate; grass, mugwort, mold (alternaria), and mold (cladosporium) are low.
Pollen Tomorrow
Tomorrow (7 October 2026) mold (alternaria) remains low, mold (cladosporium) remains low, ragweed declining, grass no longer expected, mugwort no longer expected.
7-Day Trend
Over the next week grass and mugwort will increase; ragweed, mold (alternaria), and mold (cladosporium) will decrease.
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Pollen Risk
Today - 6 October
| 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 | 5/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Low | 1/100 |
| Ragweed (Ambrosia) | Moderate | 27/100 |
| Alternaria | Low | 8/100 |
| Cladosporium | Low | 8/100 |
Tomorrow - 7 October
| 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) | None | 0/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | Low | 22/100 | |
| Alternaria | Low | 7/100 | |
| Cladosporium | Low | 9/100 |
Local Environmental Conditions
This location in Foster City is surrounded mainly by open water, with some built-up land. With much of the immediate area made up of open water, local pollen production is limited, though pollen can still drift in from surrounding land. Among allergenic trees in the wider area, oak is the main source. Grasses, plantain and pigweed growing in the surroundings are the main non-tree sources of pollen.
Oak leads the season in early summer, as temperatures climb to around 15°C, and tree pollen reaches its peak. Grass pollen follows, peaking in early fall and easing off by mid-fall. Later, plantain and pigweed keep weed pollen in the air from early summer into mid-fall. Winter is the wettest time of year, and heavy showers can bring short breaks in pollen.
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Frequently Asked Questions About Pollen in California
Is pollen high in Foster City right now?
On 6 October 2026, overall pollen levels in Foster City are moderate. Ambrosia is the main contributor to airborne pollen, while artemisia and grass remain at lower levels
Will pollen levels change in Foster City tomorrow?
On 7 October 2026, pollen conditions in Foster City will be different from today, with ambrosia continuing to decline
Is pollen expected to decrease in Foster City this week?
According to the five-day outlook, ambrosia pollen levels are expected to gradually decrease, while artemisia and grass pollen will increase, suggesting mixed conditions later in the week.
Which pollen types are currently active in Foster City?
On 6 October 2026, Ambrosia is the dominant pollen source in Foster City. artemisia and grass are also present but at lower levels.
When is pollen season in Foster City?
How often is the Foster City pollen forecast updated?
The Foster City pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Foster City 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 Foster City 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 Foster City, 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 pollen scores represent risk levels, not direct pollen measurements. Higher scores indicate higher risk.
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).
