Median AQI
61
Moderate
California · County air quality · 2025
Kern County, California
Median AQI 61 (Moderate). 23.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 61
- Median AQI
- 23.8%
- Good-air days
- 0
- Unhealthy days
- 1%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Kern County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 61 with 23.8% of 273 monitored days in the Good band, driven mainly by Ozone.
- 61
- median AQI · Moderate
- 23.8%
- days rated Good
- Ozone
- main pollutant
- 1%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 143.
Data updated July 2026
- Good · 65 d · 23.8%
- Moderate · 183 d · 67.0%
- USG · 25 d · 9.2%
How did Kern County's air break down in 2025?
Across 273 monitored days, 65 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 143 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 61 (Moderate).
Insights: Kern County, California. EPA monitors recorded a median Air Quality Index of 61 across 273 measured days in 2025, earning a Moderate classification and a Very Poor health grade. Of those days, 65 (24%) fell in the Good band (AQI 0–50), 183 (67%) registered Moderate readings, and 25 (9%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 100, while the worst single-day peak hit 143 (USG). Residents averaged about 7.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (150 days), PM2.5 (117 days), PM10 (6 days). Across the 2020–2025 trend window, good days shifted by +9 and the median AQI moved -22 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 143, usg 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
23.8%
65 of 273 monitored days
-51.2pp vs 75% target
Max AQI Recorded
143
USG
Health Grade
Very Poor
90th-pct AQI 100
Kern County, Good days share 23.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Kern 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 273 monitored days across EPA AQI categories.
Good
65
24%
Moderate
183
67%
USG
25
9%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Kern County.
- Ozone · 150 days · 54.9%
- PM2.5 · 117 days · 42.9%
- PM10 · 6 days · 2.2%
Health Impact Assessment
Very Poor
Kern County's air quality is rated Very Poor based on 23.8% good air days. No unhealthy air days were recorded in 2025.
Air quality is acceptable most days, but 25 days reached "Unhealthy for Sensitive Groups" (AQI 101-150). Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 150 of 273 monitored days.
5-Year Air Quality Trend
Air quality is improving in Kern County. Best year: 2023 (85 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 56 | 180 | 98 | 28 | 83 | 267 |
| 2021 | 35 | 202 | 97 | 29 | 84 | 314 |
| 2022 | 47 | 196 | 109 | 12 | 80 | 289 |
| 2023 | 85 | 210 | 58 | 12 | 69 | 174 |
| 2024 | 76 | 196 | 73 | 21 | 72 | 177 |
| 2025 | 65 | 183 | 25 | 0 | 61 | 143 |
How does Kern County compare?
How Kern County compares
Good-day share worse than US avg
Kern County 23.8%
Amador County, California 84.8%
US average 76.5%
Median AQI worse than US avg
Kern County 61
Amador County, California 40
US average 38
Unhealthy days / yr about average
Kern 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 Kern County.
Bernalillo County, New Mexico
AQI 59 · 23.7% good
Harris County, Texas
AQI 63 · 8.8% good
Tulare County, California
AQI 59 · 29.7% good
Clark County, Nevada
AQI 64 · 25.6% good
Imperial County, California
AQI 64 · 27.4% good
Pinal County, Arizona
AQI 66 · 24.6% good
What Kern 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 61 means for exposure. Health guidance
- See how Kern County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Kern County with its California neighbours before drawing a conclusion about the region. All of California
Based on 273 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 Kern County, California? ▼
Kern County has a median Air Quality Index (AQI) of 61, rated "Moderate." 23.8% of monitored days (65 out of 273) had good air quality in 2025.
What is the main pollutant in Kern County? ▼
The primary pollutant in Kern County is Ozone (O3), which was the main AQI driver on 150 days (55% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Kern County have? ▼
In 2025, Kern County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 143.
Is the air quality in Kern County getting better or worse? ▼
Air quality in Kern County is improving based on 5-year trends (2020-2025). Best year: 2023 with 85 good days. Worst year: 2021 with 35 good days.
What does AQI 61 mean for health? ▼
Kern County's median AQI of 61 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 Kern County compare to other counties in California? ▼
Kern County has 23.8% 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 Kern County? ▼
The 90th percentile AQI for Kern County is 100, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 143 (USG).
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.