Fort Collins pollen forecast - today, tomorrow and the week ahead
Pollen Today
Today (20 September) pollen in Fort Collins is moderate; ragweed is moderate; mugwort is low.
Pollen Tomorrow
Tomorrow (21 September 2026) mugwort remains low, ragweed remains moderate, grass 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) | Low | 2/100 |
| Ragweed (Ambrosia) | Moderate | 47/100 |
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) | Low | 1/100 | |
| Willow (Salicaceae) | None | 0/100 | — |
| Mugwort (Artemisia) | Low | 5/100 | |
| Ragweed (Ambrosia) | Moderate | 49/100 |
Local Environmental Conditions
Fort Collins' parks, including City Park and the Cache la Poudre River corridor, feature cottonwood, ash, and oak as the main tree pollen sources, with exposure varying between these green areas and the more built-up city centre. Surrounding Colorado farmland and the Rocky Mountain foothills contribute substantial grass and tree pollen, while the valley setting channels airflows and concentrates pollen across the city.
Fort Collins' pollen season opens with elm and cottonwood from late February, followed by oak and ash through April and May. Grass pollen peaks through June and July. The Cache la Poudre valley channels airflows and concentrates pollen, while surrounding Colorado farmland and the Rocky Mountain foothills contribute substantial grass and tree pollen. The semi-arid climate means fewer rainfall interruptions than in eastern US cities during the season.
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Frequently Asked Questions About Pollen in Colorado
Is pollen high in Fort Collins right now?
On 20 September 2026, overall pollen levels in Fort Collins are moderate. Ambrosia is the main contributor to airborne pollen, while artemisia remain at lower levels
Will pollen levels change in Fort Collins tomorrow?
On 21 September 2026, pollen conditions in Fort Collins will be different from today, with ambrosia at moderate levels, artemisia at low levels, grass at low levels
Is pollen expected to decrease in Fort Collins 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 Fort Collins?
On 20 September 2026, Ambrosia is the dominant pollen source in Fort Collins. artemisia are also present but at lower levels. grass are not currently active.
When is pollen season in Fort Collins?
How often is the Fort Collins pollen forecast updated?
The Fort Collins pollen forecast is updated four times daily. See the timestamp below for the most recent update.
Does pollen in Fort Collins 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 Fort Collins 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 Fort Collins, 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).
