Median AQI
31
Good
Hawaii · County air quality · 2025
Honolulu County, Hawaii
Median AQI 31 (Good). 95.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 31
- Median AQI
- 95.0%
- Good-air days
- 0
- Unhealthy days
- 89%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Honolulu County's air is good on balance, cleaner than most US counties, a median AQI of 31 with 95.0% of 182 monitored days in the Good band, driven mainly by Ozone.
- 31
- median AQI · Good
- 95.0%
- days rated Good
- Ozone
- main pollutant
- 89%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 59.
Data updated July 2026
- Good · 173 d · 95.1%
- Moderate · 9 d · 4.9%
How did Honolulu County's air break down in 2025?
Across 182 monitored days, 173 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 59 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 182 days monitored. Median AQI: 31 (Good).
Insights: Honolulu County, Hawaii. EPA monitors recorded a median Air Quality Index of 31 across 182 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 173 (95%) fell in the Good band (AQI 0–50), 9 (5%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 43, while the worst single-day peak hit 59 (Moderate). Residents averaged about 28.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (122 days), PM2.5 (59 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -190 and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 59, moderate but never Unhealthy. Nearby counties show comparable readings: Hawaii (81.1% good, AQI 30); Maui (96.1% good, AQI 22).
Air Quality Summary
Good Days
95.0%
173 of 182 monitored days
20.0pp vs 75% target
Max AQI Recorded
59
Moderate
Health Grade
Excellent
90th-pct AQI 43
Honolulu County, Good days share 95.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Honolulu 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 182 monitored days across EPA AQI categories.
Good
173
95%
Moderate
9
5%
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 Honolulu County.
- Ozone · 122 days · 67.0%
- PM2.5 · 59 days · 32.4%
- CO · 1 days · 0.5%
Health Impact Assessment
Excellent
Honolulu County's air quality is rated Excellent based on 95.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 95.0% of monitored days in 2025, with a median AQI of 31. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 122 of 182 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Honolulu County. Best year: 2021 (364 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 363 | 3 | 0 | 0 | 28 | 63 |
| 2021 | 364 | 1 | 0 | 0 | 28 | 58 |
| 2022 | 356 | 9 | 0 | 0 | 29 | 57 |
| 2023 | 337 | 27 | 1 | 0 | 31 | 117 |
| 2024 | 360 | 6 | 0 | 0 | 31 | 85 |
| 2025 | 173 | 9 | 0 | 0 | 31 | 59 |
How does Honolulu County compare?
How Honolulu County compares
Good-day share better than US avg
Honolulu County 95.0%
Hawaii County, Hawaii 81.1%
US average 76.5%
Median AQI better than US avg
Honolulu County 31
Hawaii County, Hawaii 30
US average 38
Unhealthy days / yr about average
Honolulu County 0
Hawaii County, Hawaii 0
US average 0
Other Counties in Hawaii
Air quality comparison for nearby counties in Hawaii.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Honolulu County.
Bannock County, Idaho
AQI 31 · 91.5% good
Clark County, Washington
AQI 31 · 89.3% good
Erie County, Pennsylvania
AQI 31 · 81.4% good
Josephine County, Oregon
AQI 31 · 76.2% good
Monroe County, Wisconsin
AQI 31 · 75.2% good
Montgomery County, Tennessee
AQI 31 · 84.7% good
What Honolulu 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 31 means for exposure. Health guidance
- See how Honolulu County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Honolulu County with its Hawaii neighbours before drawing a conclusion about the region. All of Hawaii
Based on 182 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 Honolulu County, Hawaii? ▼
Honolulu County has a median Air Quality Index (AQI) of 31, rated "Good." 95.0% of monitored days (173 out of 182) had good air quality in 2025.
What is the main pollutant in Honolulu County? ▼
The primary pollutant in Honolulu County is Ozone (O3), which was the main AQI driver on 122 days (67% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Honolulu County have? ▼
In 2025, Honolulu County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 59.
Is the air quality in Honolulu County getting better or worse? ▼
Air quality in Honolulu County is worsening based on 5-year trends (2020-2025). Best year: 2021 with 364 good days. Worst year: 2025 with 173 good days.
What does AQI 31 mean for health? ▼
Honolulu County's median AQI of 31 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Honolulu County compare to other counties in Hawaii? ▼
Honolulu County has 95.0% good air days. Nearby counties in Hawaii: Hawaii (81.1% good), Maui (96.1% good).
What is the 90th percentile AQI in Honolulu County? ▼
The 90th percentile AQI for Honolulu County is 43, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 59 (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.
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.