San Marcos pollen forecast - today, tomorrow and the week ahead
Today (9 August) pollen in San Marcos 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 cypress, grass, mugwort, and ragweed will increase. Forecasts are calculated by Airmine using satellites to map local vegetation and determine pollen season onset.
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San Marcos' parks and the San Marcos Creek corridor feature oak, eucalyptus, and introduced trees as the main pollen sources, with exposure varying between these green areas and the more built-up city centre. Surrounding San Diego County chaparral and the Palomar Mountain foothills contribute substantial grass and scrub pollen, while the enclosed inland valley concentrates pollen under prevailing offshore winds.
Today - 9 August
-
Alder (Alnus):
None
0/100
-
Birch (Betula):
None
0/100
-
Hazel (Corylus):
None
0/100
-
Cypress (Cupressaceae):
Low
2/100
-
Grass (Poaceae):
Low
14/100
-
Willow (Salicaceae):
None
0/100
-
Mugwort (Artemisia):
Medium
37/100
-
Ragweed (Ambrosia):
Medium
34/100
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
13/100
-
Willow (Salicaceae):
None
0/100
-
Mugwort (Artemisia):
Medium
34/100
-
Ragweed (Ambrosia):
Medium
33/100
Air quality in San Marcos
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Frequently Asked Questions
Is pollen high in San Marcos right now?
On 9 August 2026, overall pollen levels in San Marcos are moderate. Ambrosia is the main contributor to airborne pollen, while artemisia, cypress, and grass remain at lower levels
Will pollen levels change in San Marcos tomorrow?
On 10 August 2026, pollen conditions in San Marcos will be different from today, with ambrosia at medium levels, artemisia at medium levels, grass at low levels
Is pollen expected to decrease in San Marcos this week?
According to the five-day outlook, ambrosia, artemisia, cypress, and grass pollen levels will increase later in the week.
Which pollen types are currently active in San Marcos?
On 9 August 2026, Ambrosia is the dominant pollen source in San Marcos. artemisia, cypress, and grass are also present but at lower levels.
When is pollen season in San Marcos?
How often is the San Marcos pollen forecast updated?
The San Marcos pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in San Marcos 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 San Marcos 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 San Marcos, 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?
Check pollen in other popular cities:
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 San Marcos.
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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.