Fort Collins, CO Air Quality Index (AQI)
This page shows the live Air Quality Index for Fort Collins, CO (Larimer County, pop. 169,810), using AirNow's reported number and the 2024 EPA standard. Peak smoke risk here runs mid-summer into fall, when Western wildfires and long-range plumes settle into the valleys.
About air quality in Fort Collins
Fort Collins is the 3rd most populous of the 5 Colorado cities we track, with a population of about 169,810, in Larimer County.
Smoke risk here concentrates in July through September, driven by fires across the northern Rockies and the Great Basin, with terrain that traps smoke overnight and clears it by afternoon. Outside that window an elevated reading in Fort Collins is more likely to be local — traffic, dust, or a temperature inversion holding everyday pollution near the ground — than wildfire smoke, and the dominant pollutant shown above is what tells the two apart.
How local is this reading? The AQI above is reported for a monitoring area, not for a street address. The nearest city we track is Boulder, CO, about 41 miles away — close enough that the two usually move together, so a large gap between them is a sign the plume edge is somewhere between you.
Today & tomorrow
What each level means
| AQI | Level | What to do |
|---|---|---|
| 0–50 | Good | A great day to be active outside. |
| 51–100 | Moderate | Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors and watch for symptoms. |
| 101–150 | Unhealthy for Sensitive Groups | Sensitive groups should reduce prolonged or heavy exertion outdoors, take more breaks, and reschedule strenuous activities. |
| 151–200 | Unhealthy | Everyone should reduce prolonged or heavy exertion outdoors; sensitive groups should move activities indoors or reschedule. |
| 201–300 | Very Unhealthy | Everyone should avoid prolonged or heavy exertion and move activities indoors; sensitive groups should stay indoors and keep activity low. |
| 301–500 | Hazardous | Everyone should avoid all physical activity outdoors; stay indoors with clean air and keep activity low. |
Guidance paraphrased from EPA. Not medical advice — see disclaimer.
Nearby cities
All Colorado cities · Smoke & your health · Can I go outside?
Fort Collins air quality FAQ
What is the air quality in Fort Collins right now?
The live AQI for Fort Collins, CO is shown at the top of this page, sourced from AirNow (U.S. EPA) and computed with the 2024 EPA standard, with the observation time and source labeled.
Is it safe to go outside in Fort Collins today?
It depends on the current AQI and whether you're in a sensitive group. At AQI 101–150 sensitive groups should cut back on prolonged outdoor exertion; at 151+ everyone should. Use our "Can I go outside?" tool for tailored guidance.
Why does Fort Collins's AQI here match AirNow?
Because AirNow is our display truth for US monitors — we show its reported number, never a self-computed value that disagrees with it for the same monitor.
When is wildfire smoke worst in Colorado?
In the West, smoke risk peaks mid-summer through fall during active fire season and can linger in valleys.