California · County air quality · 2025
Solano County, California
Median AQI 33 (Good). 99.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 33
- Median AQI
- 99.2%
- Good-air days
- 0
- Unhealthy days
- 99%
- Cleaner than US counties
Solano County's 2025 annual median AQI is 33 (Good), with 99.2% Good days
According to the U.S. EPA Air Quality System, Solano County, California posted a 2025 median AQI of 33 (Good) across 356 monitored days, with 99.2% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Solano County's 99.2% Good-day share places it cleaner than 99% of US counties in 2025.
- Closest median-AQI peer
- Apache County (86.2% Good, median AQI 33) is the closest nationwide median-AQI peer to Solano County.
- 2020–2025 trend
- Solano County's floor-qualifying Good-day share is improving from 2020 to 2025 (50.1% → 99.2%).
- Median AQI
- Median AQI: 33
According to the 2025 EPA AQS county release on PlainAirData, Solano County, California ranks #123 of 951 by median AQI (33) and #12 by good-day share (99.2%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Solano County's Good-day share rose from 94.0% to 99.2% between the 2024 and 2025 EPA annual releases, a change of +5.2 percentage points.
- Solano County's peak single-day AQI fell from 80 to 61 between the 2024 and 2025 EPA annual releases, a change of -19 points.
- Solano County's median AQI fell from 36 to 33 between the 2024 and 2025 EPA annual releases, a change of -3 points.
Data updated August 2026
- Good · 353 d · 99.2%
- Moderate · 3 d · 0.8%
How did Solano County's air break down in 2025?
Across 356 monitored days, 353 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 →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Solano County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Solano County's Good-day share is 99.2% - cleaner than 99% of that comparison set.
Solano County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
99.2% Cleaner than 99% higher than 99% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Solano County.
- Ozone · 355 days · 99.7%
- PM10 · 1 days · 0.3%
2024 daily-monitor rhythm in Solano County
Month-by-month median AQI from EPA day-level county monitors (365 reported days in 2024). Apr posted the highest typical readings (median AQI 39, peak 61); Dec was cleanest at median 27. Summer months (Jun–Aug) averaged median AQI 36 vs 32 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,826 daily readings show a recurring local pattern: Sep has the highest matched-month median AQI (49), while Jun is lowest (36). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Solano County's air quality is rated Excellent based on 99.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 99.2% of monitored days in 2025, with a median AQI of 33. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 355 of 356 monitored days.
5-Year Air Quality Trend
Air quality is improving in Solano County. Highest Good-day share: 2025 (99.2%, 353 of 356 monitored 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 | 353 | 3 | 0 | 0 | 33 | 61 |
How does Solano County compare?
How Solano County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Solano County, California · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.