Hulett C. Merritt Mansion, Pasadena, California Pollen Forecast - Today, Tomorrow and the Week Ahead
Pollen Today
Today (10 October) pollen in Hulett C. Merritt Mansion, Pasadena, California is moderate; ragweed is moderate.
Pollen Tomorrow
Tomorrow (11 October 2026) levels are similar to today.
7-Day Trend
Over the next week grass, mugwort, and ragweed will increase.
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Pollen Risk
Today - 10 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) | None | 0/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | None | 0/100 |
| Ragweed (Ambrosia) | Moderate | 41/100 |
Tomorrow - 11 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) | Moderate | 35/100 |
Local Environmental Conditions
Built-up land and woodland share the area around this part of Pasadena, California. A nearby park adds mown lawns and planted trees to the local pollen mix. Of the allergenic trees nearby, oak matters most, while plane tree also contributes. Grasses also feature strongly, alongside mugwort among the weeds. Compared with most places, oak is especially widespread here, which makes it one of the key local allergens.
Tree pollen peaks in mid-spring, when the weather warms to around 15°C and oak and plane tree are in full flower. Grass pollen follows, peaking in late spring and easing off by early fall. Mugwort brings a final peak through summer. The oak period in mid-spring is usually the most intense time of year here.
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Frequently Asked Questions About Pollen in California
Is pollen high in Pasadena, California right now?
On 10 October 2026, overall pollen levels in Pasadena, California are moderate. Ambrosia is the main contributor to airborne pollen
Will pollen levels change in Pasadena, California tomorrow?
On 11 October 2026, pollen conditions in Pasadena, California will be similar to today, with ambrosia at moderate levels
Is pollen expected to decrease in Pasadena, California this week?
According to the five-day outlook, artemisia, grass, and ambrosia pollen levels will increase later in the week.
Which pollen types are currently active in Pasadena, California?
On 10 October 2026, Ambrosia is the dominant pollen source in Pasadena, California. artemisia and grass are not currently active.
When is pollen season in Pasadena, California?
How often is the Pasadena, California pollen forecast updated?
The Pasadena, California pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Pasadena, California 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 Pasadena, California 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 Pasadena, California, 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. |
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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).
