Median AQI
87
Moderate
California · County air quality · 2025
Riverside County, California
Median AQI 87 (Moderate). 10.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 87
- Median AQI
- 10.6%
- Good-air days
- 33
- Unhealthy days
- 0%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Riverside County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 87 with 10.6% of 274 monitored days in the Good band, driven mainly by Ozone.
- 87
- median AQI · Moderate
- 10.6%
- days rated Good
- Ozone
- main pollutant
- 0%
- cleaner than US counties
33 days reached Unhealthy or worse; the worst single reading hit AQI 365.
Data updated July 2026
- Good · 29 d · 10.6%
- Moderate · 143 d · 52.2%
- USG · 69 d · 25.2%
- Unhealthy · 32 d · 11.7%
- Hazardous · 1 d · 0.4%
How did Riverside County's air break down in 2025?
Across 274 monitored days, 29 fell in the Good band (AQI 0–50) and 33 reached Unhealthy or worse. The worst single day peaked at AQI 365 (Hazardous).
EPA AQS →Air quality data from EPA Air Quality System (2025). 274 days monitored. Median AQI: 87 (Moderate).
Insights: Riverside County, California. EPA monitors recorded a median Air Quality Index of 87 across 274 measured days in 2025, earning a Moderate classification and a Very Poor health grade. Of those days, 29 (11%) fell in the Good band (AQI 0–50), 143 (52%) registered Moderate readings, and 69 (25%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 154, while the worst single-day peak hit 365 (Hazardous). Residents averaged about 3.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (184 days), PM2.5 (56 days), PM10 (33 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -13 and the median AQI moved +0 points, placing the multi-year trajectory at stable. Residents and visitors experienced 33 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
10.6%
29 of 274 monitored days
-64.4pp vs 75% target
Max AQI Recorded
365
Hazardous
Health Grade
Very Poor
90th-pct AQI 154
Riverside County, Good days share 10.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Riverside County, Unhealthy-or-worse share 12.0%
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
29
11%
Moderate
143
52%
USG
69
25%
Unhealthy
32
12%
Very Unhealthy
0
0%
Hazardous
1
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Riverside County.
- Ozone · 184 days · 67.2%
- PM2.5 · 56 days · 20.4%
- PM10 · 33 days · 12.0%
- CO · 1 days · 0.4%
Health Impact Assessment
Very Poor
Riverside County's air quality is rated Very Poor based on 10.6% good air days. There were 33 unhealthy days in 2025 when outdoor activity should be limited.
Air quality posed significant health risk in 2025. Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, pregnant women, and adults over 65, should monitor AirNow.gov alerts and limit outdoor activity on Unhealthy (AQI 151+) and Very Unhealthy (201+) days. Peak readings reached AQI 365, well into the Hazardous range.
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 184 of 274 monitored days.
5-Year Air Quality Trend
Air quality is stable in Riverside County. Best year: 2023 (62 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 42 | 179 | 98 | 36 | 87 | 584 |
| 2021 | 19 | 210 | 89 | 44 | 89 | 329 |
| 2022 | 41 | 198 | 86 | 31 | 77 | 1683 |
| 2023 | 62 | 187 | 73 | 33 | 79 | 660 |
| 2024 | 43 | 176 | 80 | 60 | 87 | 213 |
| 2025 | 29 | 143 | 69 | 32 | 87 | 365 |
How does Riverside County compare?
How Riverside County compares
Good-day share worse than US avg
Riverside County 10.6%
Amador County, California 84.8%
US average 76.5%
Median AQI worse than US avg
Riverside County 87
Amador County, California 40
US average 38
Unhealthy days / yr worse than US avg
Riverside County 33
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 Riverside County.
San Bernardino County, California
AQI 90 · 12.4% 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 Riverside County's air means for you
On most days the air here is fine, but Ozone drives 33 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 87 means for exposure. Health guidance
- See how Riverside County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Riverside 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 Riverside County, California? ▼
Riverside County has a median Air Quality Index (AQI) of 87, rated "Moderate." 10.6% of monitored days (29 out of 274) had good air quality in 2025.
What is the main pollutant in Riverside County? ▼
The primary pollutant in Riverside County is Ozone (O3), which was the main AQI driver on 184 days (67% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Riverside County have? ▼
In 2025, Riverside County recorded 33 unhealthy air days (32 Unhealthy, 0 Very Unhealthy, 1 Hazardous). The maximum AQI reached 365.
Is the air quality in Riverside County getting better or worse? ▼
Air quality in Riverside County is stable based on 5-year trends (2020-2025). Best year: 2023 with 62 good days. Worst year: 2021 with 19 good days.
What does AQI 87 mean for health? ▼
Riverside County's median AQI of 87 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 Riverside County compare to other counties in California? ▼
Riverside County has 10.6% 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 Riverside County? ▼
The 90th percentile AQI for Riverside County is 154, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 365 (Hazardous).
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.