Caldwell pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Caldwell is high; ragweed is high; grass and mugwort are moderate.
Pollen Tomorrow
Tomorrow (21 September 2026) levels are similar to today.
7-Day Trend
Over the next week grass, mugwort, and ragweed will decrease.
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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) | Moderate | 49/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | Moderate | 32/100 |
| 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 | 50/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | Moderate | 33/100 | |
| Ragweed (Ambrosia) | High | 70/100 |
Local Environmental Conditions
Caldwell's Treasure Valley Idaho setting features cottonwood, Russian olive, and sagebrush as the main pollen sources, with exposure varying between the irrigated residential and agricultural areas along the Boise River and the surrounding high desert. The Boise River corridor is a particularly significant local source, while the stark contrast between the irrigated valley floor vegetation and the surrounding native sagebrush steppe creates the most distinctive local pollen variation across the city.
Caldwell's Treasure Valley Idaho setting produces a season opening in March with sagebrush and elm before grass from surrounding Snake River Plain farmland peaks through May and June. Mugwort from surrounding high desert landscape extends exposure into September, while the dry continental climate means fewer rainfall interruptions than in Pacific-facing cities and the Boise River valley channels airflows through the city.
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Frequently Asked Questions About Pollen in Idaho
Is pollen high in Caldwell right now?
On 20 September 2026, overall pollen levels in Caldwell are high. Ambrosia is the main contributor to airborne pollen, while artemisia and grass remain at lower levels
Will pollen levels change in Caldwell tomorrow?
On 21 September 2026, pollen conditions in Caldwell will be similar to today, with ambrosia at high levels, artemisia at moderate levels, grass at moderate levels
Is pollen expected to decrease in Caldwell this week?
According to the five-day outlook, ambrosia, artemisia, and grass pollen levels are expected to gradually decrease, suggesting improving conditions later in the week.
Which pollen types are currently active in Caldwell?
On 20 September 2026, Ambrosia is the dominant pollen source in Caldwell. artemisia and grass are also present but at lower levels.
When is pollen season in Caldwell?
How often is the Caldwell pollen forecast updated?
The Caldwell pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Caldwell 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 Caldwell 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 Caldwell, 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).
