Median AQI
47
Good
California · County air quality · 2025
Yolo County, California
Median AQI 47 (Good). 58.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 47
- Median AQI
- 58.4%
- Good-air days
- 0
- Unhealthy days
- 13%
- Cleaner than US counties
Yolo County's 2025 annual median AQI is 47 (Good), with 58.4% Good days
According to the U.S. EPA Air Quality System, Yolo County, California posted a 2025 median AQI of 47 (Good) across 365 monitored days, with 58.4% 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
- Yolo County's 58.4% Good-day share places it cleaner than 13% of US counties in 2025.
- Closest median-AQI peer
- Bonner County (56.2% Good, median AQI 47) is the closest nationwide median-AQI peer to Yolo County.
- 2020–2025 trend
- Yolo County's floor-qualifying Good-day share is stable from 2020 to 2025 (58.9% → 58.4%).
- Median AQI
- Median AQI: 47
The verdict
According to EPA Air Quality System monitoring data, Yolo County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 47 with 58.4% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 47
- median AQI · Good
- 58.4%
- days rated Good
- PM2.5
- main pollutant
- 13%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 100.
Annual release change
What changed in the 2025 EPA annual release
- Yolo County's Good-day share fell from 65.0% to 58.4% between the 2024 and 2025 EPA annual releases, a change of -6.7 percentage points.
- Yolo County's peak single-day AQI fell from 118 to 100 between the 2024 and 2025 EPA annual releases, a change of -18 points.
Data updated August 2026
- Good · 213 d · 58.4%
- Moderate · 152 d · 41.6%
How did Yolo County's air break down in 2025?
Across 365 monitored days, 213 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 100 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 47 (Good).
Insights: Yolo County, California. EPA monitors recorded a median Air Quality Index of 47 across 365 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 213 (58%) fell in the Good band (AQI 0–50), 152 (42%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 63, while the worst single-day peak hit 100 (Moderate). Residents averaged about 17.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (205 days), Ozone (160 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -0.4 points and the median AQI moved +2 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 100, moderate but never Unhealthy. Nearby counties show comparable readings: Alameda (53.0% good, AQI 49); Amador (87.4% good, AQI 38); Butte (65.2% good, AQI 46); Calaveras (82.2% good, AQI 40); Colusa (79.2% good, AQI 40); Contra Costa (53.5% good, AQI 48).
Air Quality Summary
Good Days
58.4%
213 of 365 monitored days
-16.6pp vs 75% target
Max AQI Recorded
100
Moderate
Health Grade
Moderate
90th-pct AQI 63
Yolo County, Good days share 58.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
Yolo 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 365 monitored days across EPA AQI categories.
Good
213
58%
Moderate
152
42%
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 Yolo County.
- PM2.5 · 205 days · 56.2%
- Ozone · 160 days · 43.8%
Health Impact Assessment
Moderate
Yolo County's air quality is rated Moderate based on 58.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 58.4% of monitored days in 2025, with a median AQI of 47. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 205 of 365 monitored days.
5-Year Air Quality Trend
Air quality is stable in Yolo County. Highest Good-day share: 2022 (77.5%, 283 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 215 | 123 | 14 | 13 | 45 | 209 |
| 2021 | 242 | 117 | 4 | 2 | 42 | 159 |
| 2022 | 283 | 80 | 2 | 0 | 42 | 101 |
| 2023 | 246 | 117 | 2 | 0 | 43 | 108 |
| 2024 | 238 | 127 | 1 | 0 | 45 | 118 |
| 2025 | 213 | 152 | 0 | 0 | 47 | 100 |
How does Yolo County compare?
How Yolo County compares
Good-day share worse than typical
Yolo County 58.4%
Bonner County, Idaho 56.2%
Typical US county 76.0%
Median AQI worse than typical
Yolo County 47
Bonner County, Idaho 47
Typical US county 39
Unhealthy days / yr better than typical
Yolo County 0
Bonner County, Idaho 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Yolo County (47), not geographic neighbors.
Bonner County, Idaho
Median AQI 47 · 56.2% Good-day share
Calcasieu County, Louisiana
Median AQI 47 · 62.2% Good-day share
Charleston County, South Carolina
Median AQI 47 · 60.8% Good-day share
Chatham County, Georgia
Median AQI 47 · 58.6% Good-day share
DeKalb County, Georgia
Median AQI 47 · 58.4% Good-day share
Denton County, Texas
Median AQI 47 · 57.8% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Saint Clair County, Illinois
58.4% Good-day share · median AQI 47
Gwinnett County, Georgia
58.3% Good-day share · median AQI 47
Brookings County, South Dakota
58.6% Good-day share · median AQI 46
Clark County, Indiana
58.1% Good-day share · median AQI 46
Richland County, South Carolina
58.1% Good-day share · median AQI 47
Scott County, Iowa
58.9% Good-day share · median AQI 46
California counties on the map
Geographic containment only, other monitored counties in California, independent of AQI or pollutant match.
What Yolo County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 47 means for exposure. Health guidance
- See how Yolo County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Yolo County with its California neighbours before drawing a conclusion about the region. All of California
Based on 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Yolo County, California? ▼
Yolo County has a median Air Quality Index (AQI) of 47, rated "Good." 58.4% of monitored days (213 out of 365) had good air quality in 2025.
What is the main pollutant in Yolo County? ▼
The primary pollutant in Yolo County is Fine Particles (PM2.5), which was the main AQI driver on 205 days (56% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Yolo County have? ▼
In 2025, Yolo County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 100.
Is the air quality in Yolo County getting better or worse? ▼
Air quality in Yolo County is stable across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2022 at 77.5% (283 of 365 days). Lowest qualifying Good-day share: 2025 at 58.4% (213 of 365 days).
What does AQI 47 mean for health? ▼
Yolo County's median AQI of 47 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Yolo County compare to other counties in California? ▼
Yolo County has 58.4% good air days. Nearby counties in California: Alameda (53.0% good), Amador (87.4% good), Butte (65.2% good), Calaveras (82.2% good), Colusa (79.2% good), Contra Costa (53.5% good).
What is the 90th percentile AQI in Yolo County? ▼
The 90th percentile AQI for Yolo County is 63, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 100 (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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Yolo County, California · 2020–2025
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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.