Diamond Bar pollen forecast - today, tomorrow and the week ahead

Today (9 August) pollen in Diamond Bar is medium; mugwort and ragweed are medium; cypress and grass are low. Tomorrow (10 August 2026) levels are similar - grass remains low, mugwort remains medium, ragweed remains medium. Over the following five days grass, mugwort, and ragweed will increase; cypress will remain stable. Forecasts are calculated by Airmine using satellites to map local vegetation and determine pollen season onset.

Get the full experience in the Airmine app.

Download on the App Store Get it on Google Play

Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team

Follow your pollen exposure and performance with the free Airmine–Strava integration. See your pollen and air quality exposure for every Strava activity.

Learn more

Diamond Bar's eastern Los Angeles County Pomona Valley foothill setting features walnut, oak, and toyon as the main tree pollen sources, with the Southern California Black Walnut woodlands being a particularly distinctive and locally significant native pollen source. Exposure varies between the walnut woodland-covered hillsides and the more built-up commercial corridors along Diamond Bar Boulevard, while the Puente Hills topography creates downslope wind conditions that concentrate pollen in valley floor areas.

Today - 9 August

  • Alder (Alnus):

    None

    0/100

  • Birch (Betula):

    None

    0/100

  • Hazel (Corylus):

    None

    0/100

  • Cypress (Cupressaceae):

    Low

    3/100

  • Grass (Poaceae):

    Low

    7/100

  • Willow (Salicaceae):

    None

    0/100

  • Mugwort (Artemisia):

    Medium

    37/100

  • Ragweed (Ambrosia):

    Medium

    32/100

High pollen levels may trigger sneezing, itchy eyes, and congestion. Airmine's neighbourhood estimates use satellites to map local vegetation and a statistical prediction model, updated four times daily.

Tomorrow - 10 August

  • Alder (Alnus):

    None

    0/100

  • Birch (Betula):

    None

    0/100

  • Hazel (Corylus):

    None

    0/100

  • Cypress (Cupressaceae):

    None

    0/100

  • Grass (Poaceae):

    Low

    1/100

  • Willow (Salicaceae):

    None

    0/100

  • Mugwort (Artemisia):

    Medium

    30/100

  • Ragweed (Ambrosia):

    Medium

    27/100

Air quality in Diamond Bar

View air quality

Frequently Asked Questions

Is pollen high in Diamond Bar right now?

On 9 August 2026, overall pollen levels in Diamond Bar are moderate. Ambrosia is the main contributor to airborne pollen, while artemisia, cypress, and grass remain at lower levels

Will pollen levels change in Diamond Bar tomorrow?

On 10 August 2026, pollen conditions in Diamond Bar will be different from today, with ambrosia at medium levels, artemisia at medium levels, grass at low levels

Is pollen expected to decrease in Diamond Bar 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 Diamond Bar?

On 9 August 2026, Ambrosia is the dominant pollen source in Diamond Bar. artemisia, cypress, and grass are also present but at lower levels.

When is pollen season in Diamond Bar?
Diamond Bar's eastern Los Angeles County setting produces a season opening in January with olive and walnut before grass from surrounding Pomona Valley land peaks through March and April. Mugwort extends exposure into September, while the inland foothill setting means higher temperatures than in coastal cities and the Puente Hills backdrop concentrates pollen under certain downslope wind conditions throughout the season.
How often is the Diamond Bar pollen forecast updated?

The Diamond Bar pollen forecast is updated four times daily. See the timestamp below for the most recent update.

Does pollen in Diamond Bar 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 Diamond Bar 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 Diamond Bar, 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.

Want to see pollen forecasts for other cities in United States?

Atlanta Boston Chicago Dallas Houston Los Angeles Miami New York Philadelphia

Check pollen in other popular cities:

Melton Rio de Janeiro Copenhagen Athens Denpasar Rome Cape Town Barcelona London Los Angeles New York

Data provided by Airmine — Last update: 10 August 2026 at 02:34 CEST (Data is updated four times daily.)

This page provides the latest public pollen forecast for Diamond Bar.

Get the full experience in the Airmine app.

Download on the App Store Get it on Google Play

Unless explicitly made clear, the content on this site has not been paid for by external organisations and is Airmine's sole responsibility.

Disclaimer: Forecasts are provided for informational purposes only and should not be relied upon as medical advice. Actual pollen and air quality conditions may vary from the forecast. If you have allergies, asthma, or another medical condition, consult a healthcare professional. Please see our Terms of Service for important information about limitations of liability.