Median AQI
54
Moderate
California · County air quality · 2025
Fresno County, California
Median AQI 54 (Moderate). 40.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 54
- Median AQI
- 40.1%
- Good-air days
- 1
- Unhealthy days
- 3%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Fresno County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 54 with 40.1% of 304 monitored days in the Good band, driven mainly by Ozone.
- 54
- median AQI · Moderate
- 40.1%
- days rated Good
- Ozone
- main pollutant
- 3%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 157.
Data updated July 2026
- Good · 122 d · 40.1%
- Moderate · 157 d · 51.6%
- USG · 24 d · 7.9%
- Unhealthy · 1 d · 0.3%
How did Fresno County's air break down in 2025?
Across 304 monitored days, 122 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 157 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 304 days monitored. Median AQI: 54 (Moderate).
Insights: Fresno County, California. EPA monitors recorded a median Air Quality Index of 54 across 304 measured days in 2025, earning a Moderate classification and a Poor health grade. Of those days, 122 (40%) fell in the Good band (AQI 0–50), 157 (52%) registered Moderate readings, and 24 (8%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 100, while the worst single-day peak hit 157 (Unhealthy). Residents averaged about 12.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (214 days), PM2.5 (84 days), PM10 (6 days). Across the 2020–2025 trend window, good days shifted by +47 and the median AQI moved -22 points, placing the multi-year trajectory at improving. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Amador (84.8% good, AQI 40); Butte (66.1% good, AQI 47); Calaveras (73.9% good, AQI 43); Colusa (84.9% good, AQI 39); Del Norte (81.0% good, AQI 33); El Dorado (85.8% good, AQI 39).
Air Quality Summary
Good Days
40.1%
122 of 304 monitored days
-34.9pp vs 75% target
Max AQI Recorded
157
Unhealthy
Health Grade
Poor
90th-pct AQI 100
Fresno County, Good days share 40.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Fresno County, Unhealthy-or-worse share 0.3%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 304 monitored days across EPA AQI categories.
Good
122
40%
Moderate
157
52%
USG
24
8%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Fresno County.
- Ozone · 214 days · 70.4%
- PM2.5 · 84 days · 27.6%
- PM10 · 6 days · 2.0%
Health Impact Assessment
Poor
Fresno County's air quality is rated Poor based on 40.1% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 24 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 157. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 214 of 304 monitored days.
5-Year Air Quality Trend
Air quality is improving in Fresno County. Best year: 2025 (122 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 75 | 192 | 59 | 31 | 76 | 346 |
| 2021 | 62 | 221 | 63 | 17 | 68 | 278 |
| 2022 | 78 | 217 | 67 | 3 | 71 | 159 |
| 2023 | 97 | 210 | 55 | 3 | 64 | 156 |
| 2024 | 71 | 216 | 65 | 14 | 67 | 169 |
| 2025 | 122 | 157 | 24 | 1 | 54 | 157 |
How does Fresno County compare?
How Fresno County compares
Good-day share worse than US avg
Fresno County 40.1%
Amador County, California 84.8%
US average 76.5%
Median AQI worse than US avg
Fresno County 54
Amador County, California 40
US average 38
Unhealthy days / yr worse than US avg
Fresno County 1
Amador County, California 0
US average 0
Other Counties in California
Air quality comparison for nearby counties in California.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Fresno County.
Denver County, Colorado
AQI 54 · 44.2% good
Franklin County, Ohio
AQI 54 · 39.8% good
Hamilton County, Ohio
AQI 54 · 32.1% good
Hidalgo County, Texas
AQI 54 · 36.2% good
Inyo County, California
AQI 54 · 40.7% good
Larimer County, Colorado
AQI 54 · 40.1% good
What Fresno County's air means for you
On most days the air here is fine, but Ozone drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 54 means for exposure. Health guidance
- See how Fresno County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Fresno County with its California neighbours before drawing a conclusion about the region. All of California
Based on 304 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Fresno County, California? ▼
Fresno County has a median Air Quality Index (AQI) of 54, rated "Moderate." 40.1% of monitored days (122 out of 304) had good air quality in 2025.
What is the main pollutant in Fresno County? ▼
The primary pollutant in Fresno County is Ozone (O3), which was the main AQI driver on 214 days (70% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Fresno County have? ▼
In 2025, Fresno County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 157.
Is the air quality in Fresno County getting better or worse? ▼
Air quality in Fresno County is improving based on 5-year trends (2020-2025). Best year: 2025 with 122 good days. Worst year: 2021 with 62 good days.
What does AQI 54 mean for health? ▼
Fresno County's median AQI of 54 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Fresno County compare to other counties in California? ▼
Fresno County has 40.1% good air days. Nearby counties in California: Amador (84.8% good), Butte (66.1% good), Calaveras (73.9% good), Colusa (84.9% good), Del Norte (81.0% good), El Dorado (85.8% good).
What is the 90th percentile AQI in Fresno County? ▼
The 90th percentile AQI for Fresno County is 100, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 157 (Unhealthy).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.