Median AQI
90
Moderate
California · County air quality · 2025
San Bernardino County, California
Median AQI 90 (Moderate). 12.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 90
- Median AQI
- 12.4%
- Good-air days
- 42
- Unhealthy days
- 0%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, San Bernardino County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 90 with 12.4% of 274 monitored days in the Good band, driven mainly by Ozone.
- 90
- median AQI · Moderate
- 12.4%
- days rated Good
- Ozone
- main pollutant
- 0%
- cleaner than US counties
42 days reached Unhealthy or worse; the worst single reading hit AQI 207.
Data updated July 2026
- Good · 34 d · 12.4%
- Moderate · 137 d · 50.0%
- USG · 61 d · 22.3%
- Unhealthy · 38 d · 13.9%
- Very Unhealthy · 4 d · 1.5%
How did San Bernardino County's air break down in 2025?
Across 274 monitored days, 34 fell in the Good band (AQI 0–50) and 42 reached Unhealthy or worse. The worst single day peaked at AQI 207 (Very Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 274 days monitored. Median AQI: 90 (Moderate).
Insights: San Bernardino County, California. EPA monitors recorded a median Air Quality Index of 90 across 274 measured days in 2025, earning a Moderate classification and a Very Poor health grade. Of those days, 34 (12%) fell in the Good band (AQI 0–50), 137 (50%) registered Moderate readings, and 61 (22%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 164, while the worst single-day peak hit 207 (Very Unhealthy). Residents averaged about 3.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (201 days), PM2.5 (62 days), PM10 (9 days), NO2 (1 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by +1 and the median AQI moved -3 points, placing the multi-year trajectory at improving. Residents and visitors experienced 42 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
12.4%
34 of 274 monitored days
-62.6pp vs 75% target
Max AQI Recorded
207
Very Unhealthy
Health Grade
Very Poor
90th-pct AQI 164
San Bernardino County, Good days share 12.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
San Bernardino County, Unhealthy-or-worse share 15.3%
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 274 monitored days across EPA AQI categories.
Good
34
12%
Moderate
137
50%
USG
61
22%
Unhealthy
38
14%
Very Unhealthy
4
1%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in San Bernardino County.
- Ozone · 201 days · 73.4%
- PM2.5 · 62 days · 22.6%
- PM10 · 9 days · 3.3%
- NO₂ · 1 days · 0.4%
- CO · 1 days · 0.4%
Health Impact Assessment
Very Poor
San Bernardino County's air quality is rated Very Poor based on 12.4% good air days. There were 42 unhealthy days in 2025 when outdoor activity should be limited.
Air quality reached unhealthy levels on 42 days in 2025 (38 Unhealthy, 4 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is Ozone, driving AQI on 201 of 274 monitored days.
5-Year Air Quality Trend
Air quality is improving in San Bernardino County. Best year: 2023 (50 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 33 | 170 | 76 | 69 | 93 | 236 |
| 2021 | 17 | 202 | 73 | 61 | 87 | 486 |
| 2022 | 23 | 212 | 67 | 56 | 77 | 225 |
| 2023 | 50 | 197 | 67 | 44 | 71 | 214 |
| 2024 | 40 | 182 | 56 | 61 | 87 | 593 |
| 2025 | 34 | 137 | 61 | 38 | 90 | 207 |
How does San Bernardino County compare?
How San Bernardino County compares
Good-day share worse than US avg
San Bernardino County 12.4%
Amador County, California 84.8%
US average 76.5%
Median AQI worse than US avg
San Bernardino County 90
Amador County, California 40
US average 38
Unhealthy days / yr worse than US avg
San Bernardino County 42
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 San Bernardino County.
Riverside County, California
AQI 87 · 10.6% good
Los Angeles County, California
AQI 77 · 10.9% good
El Paso County, Texas
AQI 74 · 12.7% good
Maricopa County, Arizona
AQI 71 · 16.4% good
Dona Ana County, New Mexico
AQI 70 · 19.4% good
Pinal County, Arizona
AQI 66 · 24.6% good
What San Bernardino County's air means for you
On most days the air here is fine, but Ozone drives 42 unhealthy-or-worse days 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 90 means for exposure. Health guidance
- See how San Bernardino County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare San Bernardino County with its California neighbours before drawing a conclusion about the region. All of California
Based on 274 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 San Bernardino County, California? ▼
San Bernardino County has a median Air Quality Index (AQI) of 90, rated "Moderate." 12.4% of monitored days (34 out of 274) had good air quality in 2025.
What is the main pollutant in San Bernardino County? ▼
The primary pollutant in San Bernardino County is Ozone (O3), which was the main AQI driver on 201 days (73% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does San Bernardino County have? ▼
In 2025, San Bernardino County recorded 42 unhealthy air days (38 Unhealthy, 4 Very Unhealthy, 0 Hazardous). The maximum AQI reached 207.
Is the air quality in San Bernardino County getting better or worse? ▼
Air quality in San Bernardino County is improving based on 5-year trends (2020-2025). Best year: 2023 with 50 good days. Worst year: 2021 with 17 good days.
What does AQI 90 mean for health? ▼
San Bernardino County's median AQI of 90 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 San Bernardino County compare to other counties in California? ▼
San Bernardino County has 12.4% 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 San Bernardino County? ▼
The 90th percentile AQI for San Bernardino County is 164, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 207 (Very 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.