Stanislaus, California Air Quality
Stanislaus County, California (CA)
↓ Improvingover 10 years
How Stanislaus, California Air Quality Compares
Stanislaus, California's median AQI of 54is 32% worse than the national average of 41. Air quality has improved by 6 AQI points over the past decade. Residents experience an average of 31 unhealthy air days per year, above the national threshold for concern. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
Stanislaus, California Air Quality: The Full Picture
Stanislaus, California (Stanislaus County) holds an AirHistory Air Quality Grade of D (poor, scoring 46 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 6 points between 2014 (60) and 2023 (54), and the five-year median now sits at 57 — inside the "Moderate" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 161 of 365 monitored days (44% of the year), making it the controlling pollutant for the D grade. The single worst reading logged that year hit an AQI of 150 (Unhealthy for Sensitive Groups), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 93.
In 2023, Stanislaus County recorded 166 "Good" air days (45% of the 365 days with valid AQI data), 176 "Moderate" days, and 23 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 153 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 31 per year.
The decade-long trend is improving: median AQI has been dropping by roughly 0.54 points per year. The cleanest year in the record was 2019 (median AQI 52), and the most polluted was 2015 (median AQI 62). Because the data come straight from federally certified EPA monitors, these figures track the California county the monitors physically sit in rather than a city boundary.
Get Stanislaus, California's next air-quality update
Subscribe for Stanislaus, California air-quality updates by email. No spam, unsubscribe anytime.
10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days). This area has seen measurable air quality improvement over the decade.
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 54 | 93 | 150 | 166 | 176 | 23 | Ozone |
| 2022 | 57 | 95 | 166 | 108 | 234 | 23 | PM2.5 |
| 2021 | 61 | 105 | 172 | 84 | 234 | 47 | PM2.5 |
| 2020 | 60 | 102 | 195 | 131 | 198 | 37 | PM2.5 |
| 2019 | 52 | 92 | 177 | 168 | 174 | 23 | Ozone |
| 2018 | 59 | 108 | 265 | 109 | 209 | 47 | PM2.5 |
| 2017 | 61 | 112 | 185 | 127 | 175 | 63 | Ozone |
| 2016 | 59 | 103 | 164 | 102 | 221 | 43 | PM2.5 |
| 2015 | 62 | 112 | 187 | 92 | 225 | 48 | PM2.5 |
| 2014 | 60 | 114 | 164 | 112 | 194 | 59 | Ozone |
What This Means for Stanislaus County Residents
Stanislaus, California has received an Air Quality Grade of D (46/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 54 falls in the "Moderate" range.
Encouragingly, air quality here has been improving, with the median AQI dropping by 6 points over the monitoring period. This trend suggests continued investment in emission controls and cleaner energy.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 31 unhealthy air quality days per year, days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
Related Cities in California
AQI: 48 · Grade: C
AQI: 36 · Grade: B
AQI: 50 · Grade: C
AQI: 40 · Grade: B
AQI: 55 · Grade: C
AQI: 51 · Grade: C
AQI: 32 · Grade: C
AQI: 44 · Grade: C
Frequently Asked Questions
Stanislaus, California has a current median AQI of 54, which falls in the "Moderate" range. The area has received an Air Quality Grade of D (46/100) based on 10 years of EPA monitoring data.
Air quality in Stanislaus, California is improving over the past decade. The median AQI has changed by -6 points from 2014 to 2023.
Stanislaus, California averages 31 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting Stanislaus, California is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the Stanislaus County area.
Stanislaus, California averages 31 unhealthy air days per year. With frequent unhealthy air days, asthma patients should use a HEPA air purifier indoors and check AQI before any outdoor activity. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 54 (Moderate), outdoor exercise in Stanislaus, California is safe most days, though sensitive individuals should check daily AQI before intense workouts. Stanislaus, California averages 31 days per year when athletes should move workouts indoors.