Castle Rock pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Castle Rock is moderate; ragweed is moderate.
Pollen Tomorrow
Tomorrow (21 September 2026) ragweed remains moderate, mugwort at low levels.
7-Day Trend
Over the next week grass and mugwort will increase; 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) | None | 0/100 |
| Willow (Salicaceae) | None | 0/100 |
| Mugwort (Artemisia) | None | 0/100 |
| Ragweed (Ambrosia) | Moderate | 34/100 |
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) | None | 0/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | Low | 1/100 | |
| Ragweed (Ambrosia) | Moderate | 44/100 |
Local Environmental Conditions
Castle Rock's Douglas County Front Range setting features ponderosa pine, Gambel oak, and cottonwood as the main tree pollen sources, with exposure varying considerably between the ponderosa pine-covered ridges and the more built-up commercial corridors along I-25. The dramatic topographic variation between the mesa tops and the valley floor creates distinct pollen zones, with the mesa pine forests contributing substantial tree pollen locally.
Castle Rock's Front Range Colorado setting between Denver and Colorado Springs produces a season opening with elm and cottonwood in March before oak peaks through April and May. Grass from surrounding Colorado plains peaks through May and June before mugwort extends exposure into September. The elevated setting and the Douglas County landscape mean the season is more compressed than in lower elevation cities.
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Resource Hub
Pollen forecast neighborhoods 3 neighborhoods
Frequently Asked Questions About Pollen in Colorado
Is pollen high in Castle Rock right now?
On 20 September 2026, overall pollen levels in Castle Rock are moderate. Ambrosia is the main contributor to airborne pollen
Will pollen levels change in Castle Rock tomorrow?
On 21 September 2026, pollen conditions in Castle Rock will be different from today, with ambrosia at moderate levels, artemisia at low levels
Is pollen expected to decrease in Castle Rock this week?
According to the five-day outlook, ambrosia pollen levels are expected to gradually decrease, while artemisia and grass pollen will increase, suggesting mixed conditions later in the week.
Which pollen types are currently active in Castle Rock?
On 20 September 2026, Ambrosia is the dominant pollen source in Castle Rock. artemisia and grass are not currently active.
When is pollen season in Castle Rock?
How often is the Castle Rock pollen forecast updated?
The Castle Rock pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Castle Rock 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 Castle Rock 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 Castle Rock, 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).
