Median AQI
34
Good
California · County air quality · 2025
Solano County, California
Median AQI 34 (Good). 98.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 34
- Median AQI
- 98.9%
- Good-air days
- 0
- Unhealthy days
- 95%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Solano County's air is good on balance, among the cleanest 5% of US counties, a median AQI of 34 with 98.9% of 268 monitored days in the Good band, driven mainly by Ozone.
- 34
- median AQI · Good
- 98.9%
- days rated Good
- Ozone
- main pollutant
- 95%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 61.
Data updated July 2026
- Good · 265 d · 98.9%
- Moderate · 3 d · 1.1%
How did Solano County's air break down in 2025?
Across 268 monitored days, 265 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 61 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 268 days monitored. Median AQI: 34 (Good).
Insights: Solano County, California. EPA monitors recorded a median Air Quality Index of 34 across 268 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 265 (99%) fell in the Good band (AQI 0–50), 3 (1%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 42, while the worst single-day peak hit 61 (Moderate). Residents averaged about 29.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (268 days). Across the 2020–2025 trend window, good days shifted by +82 and the median AQI moved -17 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 61, moderate but never Unhealthy. 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
98.9%
265 of 268 monitored days
23.9pp vs 75% target
Max AQI Recorded
61
Moderate
Health Grade
Excellent
90th-pct AQI 42
Solano County, Good days share 98.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Solano County, Unhealthy-or-worse share 0.0%
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 268 monitored days across EPA AQI categories.
Good
265
99%
Moderate
3
1%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Solano County.
- Ozone · 268 days · 100.0%
Health Impact Assessment
Excellent
Solano County's air quality is rated Excellent based on 98.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 98.9% of monitored days in 2025, with a median AQI of 34. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 268 of 268 monitored days.
5-Year Air Quality Trend
Air quality is improving in Solano County. Best year: 2024 (343 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 183 | 167 | 9 | 6 | 51 | 228 |
| 2021 | 215 | 147 | 3 | 0 | 44 | 126 |
| 2022 | 235 | 130 | 0 | 0 | 43 | 93 |
| 2023 | 269 | 95 | 1 | 0 | 40 | 105 |
| 2024 | 343 | 22 | 0 | 0 | 36 | 80 |
| 2025 | 265 | 3 | 0 | 0 | 34 | 61 |
How does Solano County compare?
How Solano County compares
Good-day share better than US avg
Solano County 98.9%
Amador County, California 84.8%
US average 76.5%
Median AQI better than US avg
Solano County 34
Amador County, California 40
US average 38
Unhealthy days / yr about average
Solano County 0
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 Solano County.
Belknap County, New Hampshire
AQI 34 · 87.9% good
Dyer County, Tennessee
AQI 34 · 79.4% good
Flagler County, Florida
AQI 34 · 97.4% good
Grant County, Oregon
AQI 34 · 66.7% good
Highlands County, Florida
AQI 34 · 93.2% good
Johnson County, Texas
AQI 34 · 91.6% good
What Solano County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 34 means for exposure. Health guidance
- See how Solano County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Solano County with its California neighbours before drawing a conclusion about the region. All of California
Based on 268 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 Solano County, California? ▼
Solano County has a median Air Quality Index (AQI) of 34, rated "Good." 98.9% of monitored days (265 out of 268) had good air quality in 2025.
What is the main pollutant in Solano County? ▼
The primary pollutant in Solano County is Ozone (O3), which was the main AQI driver on 268 days (100% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Solano County have? ▼
In 2025, Solano County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 61.
Is the air quality in Solano County getting better or worse? ▼
Air quality in Solano County is improving based on 5-year trends (2020-2025). Best year: 2024 with 343 good days. Worst year: 2020 with 183 good days.
What does AQI 34 mean for health? ▼
Solano County's median AQI of 34 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Solano County compare to other counties in California? ▼
Solano County has 98.9% 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 Solano County? ▼
The 90th percentile AQI for Solano County is 42, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 61 (Moderate).
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.