Median AQI
32
Good
California · County air quality · 2025
Del Norte County, California
Median AQI 32 (Good). 81.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 32
- Median AQI
- 81.8%
- Good-air days
- 0
- Unhealthy days
- 61%
- Cleaner than US counties
Del Norte County's 2025 annual median AQI is 32 (Good), with 81.8% Good days
According to the U.S. EPA Air Quality System, Del Norte County, California posted a 2025 median AQI of 32 (Good) across 352 monitored days, with 81.8% 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
- Del Norte County's 81.8% Good-day share places it cleaner than 61% of US counties in 2025.
- Closest median-AQI peer
- Aroostook County (83.3% Good, median AQI 32) is the closest nationwide median-AQI peer to Del Norte County.
- 2020–2025 trend
- Del Norte County's floor-qualifying Good-day share is improving from 2020 to 2025 (66.6% → 81.8%).
- Median AQI
- Median AQI: 32
The verdict
According to EPA Air Quality System monitoring data, Del Norte County's air is good on balance, cleaner than the median US county, a median AQI of 32 with 81.8% of 352 monitored days in the Good band, driven mainly by PM2.5.
- 32
- median AQI · Good
- 81.8%
- days rated Good
- PM2.5
- main pollutant
- 61%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 70.
Annual release change
What changed in the 2025 EPA annual release
- Del Norte County's peak single-day AQI fell from 125 to 70 between the 2024 and 2025 EPA annual releases, a change of -55 points.
- Del Norte County's Good-day share rose from 80.3% to 81.8% between the 2024 and 2025 EPA annual releases, a change of +1.5 percentage points.
Data updated August 2026
- Good · 288 d · 81.8%
- Moderate · 64 d · 18.2%
How did Del Norte County's air break down in 2025?
Across 352 monitored days, 288 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 70 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 352 days monitored. Median AQI: 32 (Good).
Insights: Del Norte County, California. EPA monitors recorded a median Air Quality Index of 32 across 352 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 288 (82%) fell in the Good band (AQI 0–50), 64 (18%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 54, while the worst single-day peak hit 70 (Moderate). Residents averaged about 24.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (352 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +15.7 points (measured against 292 monitored days in 2020 and 352 in 2025, so raw day counts are not comparable) and the median AQI moved -10 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 70, 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
81.8%
288 of 352 monitored days
6.8pp vs 75% target
Max AQI Recorded
70
Moderate
Health Grade
Good
90th-pct AQI 54
Del Norte County, Good days share 81.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Del Norte 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 352 monitored days across EPA AQI categories.
Good
288
82%
Moderate
64
18%
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 Del Norte County.
- PM2.5 · 352 days · 100.0%
Health Impact Assessment
Good
Del Norte County's air quality is rated Good based on 81.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 81.8% of monitored days in 2025, with a median AQI of 32. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 352 of 352 monitored days.
5-Year Air Quality Trend
Air quality is improving in Del Norte County. Highest Good-day share: 2022 (86.9%, 299 of 344 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 193 | 90 | 4 | 3 | 42 | 245 |
| 2021 | 259 | 64 | 0 | 0 | 31 | 72 |
| 2022 | 299 | 45 | 0 | 0 | 29 | 74 |
| 2023 | 268 | 52 | 6 | 2 | 32 | 187 |
| 2024 | 232 | 55 | 2 | 0 | 32 | 125 |
| 2025 | 288 | 64 | 0 | 0 | 32 | 70 |
How does Del Norte County compare?
How Del Norte County compares
Good-day share better than US avg
Del Norte County 81.8%
Aroostook County, Maine 83.3%
US average 76.0%
Median AQI better than US avg
Del Norte County 32
Aroostook County, Maine 32
US average 39
Unhealthy days / yr better than US avg
Del Norte County 0
Aroostook County, Maine 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Del Norte County (32), not geographic neighbors.
Aroostook County, Maine
Median AQI 32 · 83.3% Good-day share
Belknap County, New Hampshire
Median AQI 32 · 88.8% Good-day share
Carter County, Oklahoma
Median AQI 32 · 81.6% Good-day share
Hawaii County, Hawaii
Median AQI 32 · 86.0% Good-day share
Macon County, North Carolina
Median AQI 32 · 96.5% Good-day share
Montgomery County, Tennessee
Median AQI 32 · 83.8% 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).
Sullivan County, Tennessee
82.0% Good-day share · median AQI 40
Cedar County, Missouri
81.6% Good-day share · median AQI 39
Missoula County, Montana
81.6% Good-day share · median AQI 38
Guaynabo County, Puerto Rico
81.6% Good-day share · median AQI 33
Mitchell County, North Carolina
81.5% Good-day share · median AQI 31
Lawrence County, Tennessee
81.5% Good-day share · median AQI 33
California counties on the map
Geographic containment only, other monitored counties in California, independent of AQI or pollutant match.
What Del Norte 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 32 means for exposure. Health guidance
- See how Del Norte County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Del Norte County with its California neighbours before drawing a conclusion about the region. All of California
Based on 352 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 Del Norte County, California? ▼
Del Norte County has a median Air Quality Index (AQI) of 32, rated "Good." 81.8% of monitored days (288 out of 352) had good air quality in 2025.
What is the main pollutant in Del Norte County? ▼
The primary pollutant in Del Norte County is Fine Particles (PM2.5), which was the main AQI driver on 352 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Del Norte County have? ▼
In 2025, Del Norte County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 70.
Is the air quality in Del Norte County getting better or worse? ▼
Air quality in Del Norte 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: 2022 at 86.9% (299 of 344 days). Lowest qualifying Good-day share: 2020 at 66.6% (193 of 292 days).
What does AQI 32 mean for health? ▼
Del Norte County's median AQI of 32 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Del Norte County compare to other counties in California? ▼
Del Norte County has 81.8% 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 Del Norte County? ▼
The 90th percentile AQI for Del Norte County is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 70 (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 Del Norte 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.