San Tan Valley pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in San Tan Valley is high; mugwort and ragweed are high; grass is moderate.
Pollen Tomorrow
Tomorrow (21 September 2026) mugwort remains high, ragweed remains high, grass increasing.
7-Day Trend
Over the next week grass, mugwort, and ragweed 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) | Moderate | 44/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | High | 59/100 |
| Ragweed (Ambrosia) | High | 64/100 |
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 | 51/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | High | 65/100 | |
| Ragweed (Ambrosia) | High | 70/100 |
Local Environmental Conditions
San Tan Valley's suburban setting in the Phoenix metro area means introduced olive, mulberry, and eucalyptus trees planted across parks and residential streets are the main allergenic pollen sources, with exposure varying between these irrigated green areas and the more arid desert surroundings. Surrounding Sonoran Desert scrub and the San Tan Mountains contribute seasonal shrub and grass pollen under prevailing winds.
San Tan Valley's pollen season in the Phoenix metro area is dominated by introduced olive and mulberry from February through April, producing intense early-season tree pollen. Native Sonoran Desert species including palo verde and mesquite contribute from March through May. The long, hot, dry summer largely suppresses mid-season pollen, with a secondary grass peak possible after monsoon rains across the desert basin setting.
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Frequently Asked Questions About Pollen in Arizona
Is pollen high in San Tan Valley right now?
On 20 September 2026, overall pollen levels in San Tan Valley are high. Ambrosia is the main contributor to airborne pollen, while artemisia and grass remain at lower levels
Will pollen levels change in San Tan Valley tomorrow?
On 21 September 2026, pollen conditions in San Tan Valley will be different from today, with ambrosia at high levels, artemisia at high levels and grass increasing
Is pollen expected to decrease in San Tan Valley this week?
According to the five-day outlook, grass, ambrosia, and artemisia pollen levels are expected to gradually decrease, suggesting improving conditions later in the week.
Which pollen types are currently active in San Tan Valley?
On 20 September 2026, Ambrosia is the dominant pollen source in San Tan Valley. artemisia and grass are also present but at lower levels.
When is pollen season in San Tan Valley?
How often is the San Tan Valley pollen forecast updated?
The San Tan Valley pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in San Tan Valley 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 Tan Valley 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 Tan Valley, 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).
