Honolulu Air Quality in September
Across 2019–2025, Honolulu's September air quality had a median AQI of 22 (Good) over 210 monitored days in the Urban Honolulu, HI area. 0.0% of September days (0 of 210) reached Unhealthy for Sensitive Groups or worse, and fine particulate matter (PM2.5) set the daily AQI on 50.0% of days. The cleanest September on record here was 2022 (median AQI 20, 0 days above 100) and the worst was 2024 (median 26, 0 days above 100, peak AQI 38).
- Good: 100.0%
- Moderate: 0.0%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Honolulu in September?
Good on a typical day: median AQI 22 across 2019–2025, with 0.0% of September days above AQI 100. Fine particulate matter (PM2.5) is the main driver.
- ✓100.0% of September days were Good (AQI 0–50), 0.0% Moderate (51–100).
- ✓0 days of 210 reached AQI 101+; the September peak was 49.
- ✓Best September: 2022; worst September: 2024.
Frequently asked questions
What is the air quality like in Honolulu in September?▾
Across 2019–2025, the median daily AQI in Honolulu in September was 22 (Good). 100.0% of days were Good, 0.0% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 210 monitored days in EPA's Air Quality System.
Is September a good time for outdoor exercise in Honolulu?▾
A typical September day in Honolulu sits in the Good range (median AQI 22), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of September days reached AQI 101+ in 2019–2025.
Which pollutant causes Honolulu's September air quality problems?▾
Fine particulate matter (PM2.5) set the daily AQI on 50.0% of September days in Honolulu. The highest September AQI recorded in 2019–2025 was 49 (Good), in 2024.
Honolulu September air quality, year by year
Honolulu September air quality by year (Urban Honolulu, HI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 30 | 23 | 0 | 29 | O3 |
| 2020 | 30 | 22 | 0 | 29 | PM2.5 |
| 2021 | 30 | 22 | 0 | 47 | O3 |
| 2022cleanest | 30 | 20 | 0 | 27 | O3 |
| 2023 | 30 | 26 | 0 | 49 | PM2.5 |
| 2024worst | 30 | 26 | 0 | 38 | O3 |
| 2025 | 30 | 22 | 0 | 33 | O3 |
What September air means in Honolulu
A typical September day in Honolulu sits in the Good range (median AQI 22), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of September days reached AQI 101+ in 2019–2025.
September's median AQI of 22 is below Honolulu's whole-year median of 29, making it one of the area's cleaner periods. Nationally, the median September AQI across every EPA metro area (100,699 metro-days, 2019–2025) is 43, so Honolulu runs below the national September norm; 0.0% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Honolulu's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Honolulu
The latest EPA AirNow observation puts Honolulu's AQI at 15 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Honolulu air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Urban Honolulu, HI), 2019–2025. Daily AQI per CBSA is the highest AQI reported by any monitor in the area that day; the defining parameter is the pollutant that set it. Month and season statistics pool every such day in the period across all years listed. Retrieved 2026-09-09.