Chico pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Chico is high; grass and ragweed are high; mugwort is moderate.
Pollen Tomorrow
Tomorrow (21 September 2026) levels are similar to today.
7-Day Trend
Over the next week grass and ragweed will increase; mugwort will decrease.
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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 | 52/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Moderate | 30/100 |
| 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) | High | 56/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | Moderate | 32/100 | |
| Ragweed (Ambrosia) | High | 70/100 |
Local Environmental Conditions
Chico's parks, including Bidwell Park and the Big Chico Creek corridor, feature oak, ash, and walnut as the main tree pollen sources, with exposure varying between these green areas and the more built-up city centre. Surrounding Sacramento Valley farmland and the Sierra Nevada foothills contribute substantial grass and crop pollen, while the flat, open valley landscape allows pollen to disperse readily across the city.
Chico's pollen season opens with oak and walnut from late January in the mild Sacramento Valley climate. Ash follows through February and March, with grass peaking strongly through April and May. The flat, open valley landscape and surrounding Bidwell Park woodland contribute substantial tree pollen, while the Sierra Nevada foothills contribute additional tree pollen under prevailing valley winds. The hot, dry summer largely suppresses mid-season pollen.
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Frequently Asked Questions About Pollen in California
Is pollen high in Chico right now?
On 20 September 2026, overall pollen levels in Chico are high. Ambrosia is the main contributor to airborne pollen, while grass and artemisia remain at lower levels
Will pollen levels change in Chico tomorrow?
On 21 September 2026, pollen conditions in Chico will be similar to today, with ambrosia at high levels, artemisia at moderate levels, grass at high levels
Is pollen expected to decrease in Chico this week?
According to the five-day outlook, artemisia pollen levels are expected to gradually decrease, while ambrosia and grass pollen will increase, suggesting mixed conditions later in the week.
Which pollen types are currently active in Chico?
On 20 September 2026, Ambrosia is the dominant pollen source in Chico. grass and artemisia are also present but at lower levels.
When is pollen season in Chico?
How often is the Chico pollen forecast updated?
The Chico pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Chico 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 Chico 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 Chico, 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).
