Median AQI
46
Good
California · County air quality · 2025
Butte County, California
Median AQI 46 (Good). 65.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 46
- Median AQI
- 65.2%
- Good-air days
- 0
- Unhealthy days
- 23%
- Cleaner than US counties
Butte County's 2025 annual median AQI is 46 (Good), with 65.2% Good days
According to the U.S. EPA Air Quality System, Butte County, California posted a 2025 median AQI of 46 (Good) across 365 monitored days, with 65.2% 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
- Butte County's 65.2% Good-day share places it cleaner than 23% of US counties in 2025.
- Closest median-AQI peer
- Beaver County (55.6% Good, median AQI 46) is the closest nationwide median-AQI peer to Butte County.
- 2020–2025 trend
- Butte County's floor-qualifying Good-day share is improving from 2020 to 2025 (41.3% → 65.2%).
- Median AQI
- Median AQI: 46
The verdict
According to EPA Air Quality System monitoring data, Butte County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 46 with 65.2% of 365 monitored days in the Good band, driven mainly by PM2.5.
- 46
- median AQI · Good
- 65.2%
- days rated Good
- PM2.5
- main pollutant
- 23%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 96.
Annual release change
What changed in the 2025 EPA annual release
- Butte County's peak single-day AQI fell from 213 to 96 between the 2024 and 2025 EPA annual releases, a change of -117 points.
- Butte County's Good-day share rose from 63.1% to 65.2% between the 2024 and 2025 EPA annual releases, a change of +2.1 percentage points.
- Butte County's Unhealthy-category days fell from 1 to 0 between the 2024 and 2025 EPA annual releases, a change of -1 days.
Data updated August 2026
- Good · 238 d · 65.2%
- Moderate · 127 d · 34.8%
How did Butte County's air break down in 2025?
Across 365 monitored days, 238 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 96 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 365 days monitored. Median AQI: 46 (Good).
Insights: Butte County, California. EPA monitors recorded a median Air Quality Index of 46 across 365 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 238 (65%) fell in the Good band (AQI 0–50), 127 (35%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 61, while the worst single-day peak hit 96 (Moderate). Residents averaged about 19.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (192 days), Ozone (173 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +24.5 points and the median AQI moved -8 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 96, moderate but never Unhealthy. Nearby counties show comparable readings: Alameda (53.0% good, AQI 49); Amador (87.4% good, AQI 38); Calaveras (82.2% good, AQI 40); Colusa (79.2% good, AQI 40); Contra Costa (53.5% good, AQI 48); Del Norte (81.8% good, AQI 32).
Air Quality Summary
Good Days
65.2%
238 of 365 monitored days
-9.8pp vs 75% target
Max AQI Recorded
96
Moderate
Health Grade
Moderate
90th-pct AQI 61
Butte County, Good days share 65.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
Butte 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
238
65%
Moderate
127
35%
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 Butte County.
- PM2.5 · 192 days · 52.6%
- Ozone · 173 days · 47.4%
Health Impact Assessment
Moderate
Butte County's air quality is rated Moderate based on 65.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 65.2% of monitored days in 2025, with a median AQI of 46. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 192 of 365 monitored days.
5-Year Air Quality Trend
Air quality is improving in Butte County. Highest Good-day share: 2025 (65.2%, 238 of 365 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 149 | 178 | 18 | 16 | 54 | 508 |
| 2021 | 160 | 174 | 18 | 10 | 53 | 257 |
| 2022 | 191 | 171 | 3 | 0 | 50 | 119 |
| 2023 | 191 | 174 | 0 | 0 | 50 | 100 |
| 2024 | 231 | 133 | 0 | 1 | 46 | 213 |
| 2025 | 238 | 127 | 0 | 0 | 46 | 96 |
How does Butte County compare?
How Butte County compares
Good-day share worse than typical
Butte County 65.2%
Beaver County, Pennsylvania 55.6%
Typical US county 76.0%
Median AQI worse than typical
Butte County 46
Beaver County, Pennsylvania 46
Typical US county 39
Unhealthy days / yr better than typical
Butte County 0
Beaver County, Pennsylvania 0
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Butte County (46), not geographic neighbors.
Beaver County, Pennsylvania
Median AQI 46 · 55.6% Good-day share
Brookings County, South Dakota
Median AQI 46 · 58.6% Good-day share
Buchanan County, Missouri
Median AQI 46 · 56.4% Good-day share
Clark County, Indiana
Median AQI 46 · 58.1% Good-day share
Clarke County, Georgia
Median AQI 46 · 57.8% Good-day share
Coconino County, Arizona
Median AQI 46 · 70.1% 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).
Delaware County, Pennsylvania
65.2% Good-day share · median AQI 44
Blue Earth County, Minnesota
65.3% Good-day share · median AQI 42
Florence County, South Carolina
65.1% Good-day share · median AQI 44
Hamilton County, Tennessee
64.9% Good-day share · median AQI 44
Macon County, Illinois
64.9% Good-day share · median AQI 44
Camden County, New Jersey
65.6% Good-day share · median AQI 44
California counties on the map
Geographic containment only, other monitored counties in California, independent of AQI or pollutant match.
What Butte 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 46 means for exposure. Health guidance
- See how Butte County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Butte 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 Butte County, California? ▼
Butte County has a median Air Quality Index (AQI) of 46, rated "Good." 65.2% of monitored days (238 out of 365) had good air quality in 2025.
What is the main pollutant in Butte County? ▼
The primary pollutant in Butte County is Fine Particles (PM2.5), which was the main AQI driver on 192 days (53% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Butte County have? ▼
In 2025, Butte County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 96.
Is the air quality in Butte County getting better or worse? ▼
Air quality in Butte County is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2025 at 65.2% (238 of 365 days). Lowest qualifying Good-day share: 2020 at 41.3% (149 of 366 days).
What does AQI 46 mean for health? ▼
Butte County's median AQI of 46 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Butte County compare to other counties in California? ▼
Butte County has 65.2% good air days. Nearby counties in California: Alameda (53.0% good), Amador (87.4% good), Calaveras (82.2% good), Colusa (79.2% good), Contra Costa (53.5% good), Del Norte (81.8% good).
What is the 90th percentile AQI in Butte County? ▼
The 90th percentile AQI for Butte County is 61, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 96 (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 Butte 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.