San Luis Obispo pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in San Luis Obispo is high; grass and ragweed are high; mugwort is low.
Pollen Tomorrow
Tomorrow (21 September 2026) ragweed remains high, grass declining, mugwort no longer expected.
7-Day Trend
Over the next week grass, mugwort, and ragweed will increase.
Explore Forecasts
Air Quality
Pollen for Neighborhoods
Air Quality in Other Cities
Get More in Our App
Local pollen and air quality forecasts, interactive pollen maps and route profiles
Features and forecast availability vary by region.
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) | High | 56/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Low | 12/100 |
| Ragweed (Ambrosia) | High | 70/100 |
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) | Moderate | 42/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | None | 0/100 | |
| Ragweed (Ambrosia) | High | 57/100 |
Local Environmental Conditions
San Luis Obispo's setting on a valley between coastal hills on California's Central Coast supports coast live oak, chaparral on the hillsides, and eucalyptus groves as the leading local vegetation, all factoring into the pollen count through the year. Wind patterns across the area help determine how far pollen travels from these source plants. The mix of native and introduced species here is fairly typical for this part of the country.
Pollen season in San Luis Obispo starts with olive and acacia in January then eucalyptus follows, running through February. Peak grass pollen arrives in March and April, and sagebrush and mugwort extend exposure into early autumn. The Southern California Mediterranean climate advances the season, and onshore Pacific breezes can periodically disperse pollen throughout the year.
Get pollen & AQ on Strava
Follow your environmental exposure and performance with the free Airmine-Strava integration. See your pollen and air quality exposure for every Strava activity.
Resource Hub
Pollen forecast neighborhoods 16 neighborhoods
Frequently Asked Questions About Pollen in California
Is pollen high in San Luis Obispo right now?
On 20 September 2026, overall pollen levels in San Luis Obispo are high. Ambrosia is the main contributor to airborne pollen, while grass and artemisia remain at lower levels
Will pollen levels change in San Luis Obispo tomorrow?
On 21 September 2026, pollen conditions in San Luis Obispo will be different from today, with ambrosia at high levels and grass continuing to decline
Is pollen expected to decrease in San Luis Obispo 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 San Luis Obispo?
On 20 September 2026, Ambrosia is the dominant pollen source in San Luis Obispo. grass and artemisia are also present but at lower levels.
When is pollen season in San Luis Obispo?
How often is the San Luis Obispo pollen forecast updated?
The San Luis Obispo pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in San Luis Obispo 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 Luis Obispo 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 Luis Obispo, 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).
