Metro area air quality · 2025
San Luis Obispo-Paso Robles-Arroyo Grande, CA
Median AQI 50 (Good). 52.3% of monitored days rated Good across this metro's EPA monitoring network.
- 50
- Median AQI
- 52.3%
- Good-air days
- 0
- Unhealthy days
- 15%
- Cleaner than US metros
San Luis Obispo-Paso Robles-Arroyo Grande, CA posted a 2025 median AQI of 50 (Good) with 52.3% Good days
According to the U.S. EPA Air Quality System, the San Luis Obispo-Paso Robles-Arroyo Grande, CA CBSA recorded a median AQI of 50 across 365 monitored days in 2025, with 52.3% 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 San Luis Obispo-Paso Robles-Arroyo Grande, CA CBSA's 52.3% Good-day share places it cleaner than 15% of US metros in 2025.
- Closest median-AQI peer
- Fort Collins, CO (50.7% Good, median AQI 50) is the closest nationwide median-AQI peer to San Luis Obispo-Paso Robles-Arroyo Grande, CA.
- 2020–2025 Good-day shift
- San Luis Obispo-Paso Robles-Arroyo Grande, CA's Good-day share moved +6.3 points from 2020 to 2025 (median AQI -3).
- Median AQI
- Median AQI: 50
Aggregated from EPA Air Quality System (2025), 365 monitored days. EPA AQS →
The verdict
San Luis Obispo-Paso Robles-Arroyo Grande, CA lands in the lower Good-day tercile (52.3% 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 52.3% of 365 monitored days in the Good band.
- 50
- median AQI · Good
- 52.3%
- days rated Good
- 15%
- cleaner than US metros
- 119
- worst single reading
No day crossed into the Unhealthy tier across the metro's monitors in 2025.
San Luis Obispo-Paso Robles-Arroyo Grande, CA lands in the lower Good-day tercile (52.3% Good), a thinner clean-air share than most CBSA peers here. Signature read: 52.3% 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 191 Good (52%), 167 Moderate (46%), and 7 Unhealthy-for-Sensitive-Groups (2%). The 90th-percentile AQI finished at 67; the highest single-day reading hit 119 (USG).
Across 2020–2025, Good-day share shifted +6.3 points and median AQI moved -3 (improving). No Unhealthy-tier days appear in this annual dataset. Metros with comparable AQI profiles include Fort Collins, CO (50.7% good, AQI 50); Madera, CA (50.4% good, AQI 50); Merced, CA (51.0% good, AQI 50).
Air Quality Summary
Median AQI
50
Good
Good Days
52.3%
191 of 365 days
Max AQI
119
USG
Health Grade
Moderate
90th pct: 67
AQI Day Breakdown (2025)
Distribution of 365 monitored days across EPA AQI categories.
Good
191
52%
Moderate
167
46%
USG
7
2%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Health Impact Assessment
The San Luis Obispo-Paso Robles-Arroyo Grande, CA metro area's air quality is rated Moderate based on 52.3% 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 San Luis Obispo-Paso Robles-Arroyo Grande, CA metro compare?
How San Luis Obispo-Paso Robles-Arroyo Grande, CA compares
5-Year Air Quality Trend
Air quality is improving in the San Luis Obispo-Paso Robles-Arroyo Grande, CA metro. Highest Good-day share: 2023 (57.7%, 207 of 359 monitored days).
| Year | Good | Moderate | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|
| 2020 | 161 | 174 | 7 | 53 | 334 |
| 2021 | 154 | 203 | 0 | 53 | 133 |
| 2022 | 117 | 245 | 0 | 55 | 115 |
| 2023 | 207 | 152 | 0 | 47 | 122 |
| 2024 | 193 | 163 | 0 | 49 | 122 |
| 2025 | 191 | 167 | 0 | 50 | 119 |
Metros with a similar median AQI
CBSA peers nationwide whose annual median AQI sits near San Luis Obispo-Paso Robles-Arroyo Grande, CA (50).
Fort Collins, CO
Median AQI 50 · 50.7% Good-day share
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
Metros with similar unhealthy-day exposure
A second relationship type: metros whose unhealthy-or-worse day count is closest to San Luis Obispo-Paso Robles-Arroyo Grande, CA'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 San Luis Obispo-Paso Robles-Arroyo Grande, CA have? ▼
What is the air quality in the San Luis Obispo-Paso Robles-Arroyo Grande, CA metro area? ▼
Is air quality in San Luis Obispo-Paso Robles-Arroyo Grande, CA getting better or worse? ▼
What does AQI 50 mean for health? ▼
How does San Luis Obispo-Paso Robles-Arroyo Grande, CA compare to other metro areas? ▼
What is the 90th percentile AQI for San Luis Obispo-Paso Robles-Arroyo Grande, CA? ▼
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for San Luis Obispo-Paso Robles-Arroyo Grande, CA, 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, San Luis Obispo-Paso Robles-Arroyo Grande, CA · 2020–2025