Metro area air quality · 2025
Fort Collins, CO
Median AQI 50 (Good). 50.7% of monitored days rated Good across this metro's EPA monitoring network.
- 50
- Median AQI
- 50.7%
- Good-air days
- 0
- Unhealthy days
- 13%
- Cleaner than US metros
Fort Collins, CO posted a 2025 median AQI of 50 (Good) with 50.7% Good days
According to the U.S. EPA Air Quality System, the Fort Collins, CO CBSA recorded a median AQI of 50 across 365 monitored days in 2025, with 50.7% rated Good and 0 unhealthy or worse. This is an annual metro comparison, not a live advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US metros
- The Fort Collins, CO CBSA's 50.7% Good-day share places it cleaner than 13% of US metros in 2025.
- Closest median-AQI peer
- Madera, CA (50.4% Good, median AQI 50) is the closest nationwide median-AQI peer to Fort Collins, CO.
- 2020–2025 Good-day shift
- Fort Collins, CO's Good-day share moved -4.7 points from 2020 to 2025 (median AQI +1).
- Median AQI
- Median AQI: 50
Aggregated from EPA Air Quality System (2025), 365 monitored days. EPA AQS →
The verdict
Fort Collins, CO lands in the lower Good-day tercile (50.7% Good), a thinner clean-air share than most CBSA peers here. On the EPA scale the metro runs good, among the more polluted US metros, with a median AQI of 50 and 50.7% of 365 monitored days in the Good band.
- 50
- median AQI · Good
- 50.7%
- days rated Good
- 13%
- cleaner than US metros
- 119
- worst single reading
No day crossed into the Unhealthy tier across the metro's monitors in 2025.
Annual release change
What changed in the 2025 EPA annual release
- Fort Collins, CO metro's Good-day share rose from 45.2% to 52.3% between the 2024 and 2025 EPA annual releases, a change of +7.0 percentage points.
- Fort Collins, CO metro's peak single-day AQI fell from 161 to 119 between the 2024 and 2025 EPA annual releases, a change of -42 points.
- Fort Collins, CO metro's Unhealthy-category days fell from 2 to 0 between the 2024 and 2025 EPA annual releases, a change of -2 days.
- Fort Collins, CO metro's median AQI fell from 54 to 50 between the 2024 and 2025 EPA annual releases, a change of -4 points.
Fort Collins, CO lands in the lower Good-day tercile (50.7% Good), a thinner clean-air share than most CBSA peers here. Signature read: 50.7% Good-day share (low tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 50 over 365 measured days in 2025 (Good / Moderate). The monitored-day split lands at 185 Good (51%), 169 Moderate (46%), and 11 Unhealthy-for-Sensitive-Groups (3%). The 90th-percentile AQI finished at 84; the highest single-day reading hit 119 (USG).
Across 2020–2025, Good-day share shifted -4.7 points and median AQI moved +1 (worsening). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Madera, CA (50.4% good, AQI 50); Merced, CA (51.0% good, AQI 50); Nashville-Davidson--Murfreesboro--Franklin, TN (51.2% good, AQI 50).
Air Quality Summary
Median AQI
50
Good
Good Days
50.7%
185 of 365 days
Max AQI
119
USG
Health Grade
Moderate
90th pct: 84
AQI Day Breakdown (2025)
Distribution of 365 monitored days across EPA AQI categories.
Good
185
51%
Moderate
169
46%
USG
11
3%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Health Impact Assessment
The Fort Collins, CO metro area's air quality is rated Moderate based on 50.7% good air days. No unhealthy air days were recorded in 2025.
Air quality is generally acceptable. Unusually sensitive people should monitor real-time conditions at AirNow.gov during high-pollution events.
How does the Fort Collins, CO metro compare?
How Fort Collins, CO compares
5-Year Air Quality Trend
Air quality is worsening in the Fort Collins, CO metro. Highest Good-day share: 2020 (56.9%, 197 of 346 monitored days).
| Year | Good | Moderate | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|
| 2020 | 197 | 147 | 2 | 49 | 159 |
| 2021 | 164 | 151 | 4 | 54 | 159 |
| 2022 | 176 | 179 | 0 | 51 | 126 |
| 2023 | 175 | 185 | 1 | 51 | 156 |
| 2024 | 156 | 187 | 2 | 54 | 161 |
| 2025 | 185 | 169 | 0 | 50 | 119 |
Metros with a similar median AQI
CBSA peers nationwide whose annual median AQI sits near Fort Collins, CO (50).
Madera, CA
Median AQI 50 · 50.4% Good-day share
Merced, CA
Median AQI 50 · 51.0% Good-day share
Nashville-Davidson--Murfreesboro--Franklin, TN
Median AQI 50 · 51.2% Good-day share
Oxnard-Thousand Oaks-Ventura, CA
Median AQI 50 · 52.0% Good-day share
Reno, NV
Median AQI 50 · 50.1% Good-day share
San Luis Obispo-Paso Robles-Arroyo Grande, CA
Median AQI 50 · 52.3% Good-day share
Metros with similar unhealthy-day exposure
A second relationship type: metros whose unhealthy-or-worse day count is closest to Fort Collins, CO's 0 (independent of median AQI).
Aberdeen, SD
0 unhealthy-or-worse days · median AQI 27
Aberdeen, WA
0 unhealthy-or-worse days · median AQI 22
Adrian, MI
0 unhealthy-or-worse days · median AQI 41
Akron, OH
0 unhealthy-or-worse days · median AQI 45
Albany, GA
0 unhealthy-or-worse days · median AQI 46
Albany, OR
0 unhealthy-or-worse days · median AQI 27
Frequently Asked Questions
How many unhealthy air days does Fort Collins, CO have? ▼
What is the air quality in the Fort Collins, CO metro area? ▼
Is air quality in Fort Collins, CO getting better or worse? ▼
What does AQI 50 mean for health? ▼
How does Fort Collins, CO compare to other metro areas? ▼
What is the 90th percentile AQI for Fort Collins, CO? ▼
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Fort Collins, CO, 2025. See our methodology for how AQI, median, and coverage figures are computed.
Read our methodology , how this data is sourced, computed, and verified.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary, Fort Collins, CO · 2020–2025