Honolulu Air Quality in Fall
Across 2019–2025, Honolulu's fall (September–November) air quality had a median AQI of 26 (Good) over 637 monitored days in the Urban Honolulu, HI area. 0.0% of fall days (0 of 637) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 61.1% of days. The cleanest fall on record here was 2021 (median AQI 23, 0 days above 100) and the worst was 2024 (median 27, 0 days above 100, peak AQI 49).
- Good: 99.5%
- Moderate: 0.5%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Honolulu in fall?
Good on a typical day: median AQI 26 across 2019–2025, with 0.0% of fall days above AQI 100. Ground-level ozone is the main driver.
- ✓99.5% of fall days were Good (AQI 0–50), 0.5% Moderate (51–100).
- ✓0 days of 637 reached AQI 101+; the fall peak was 55.
- ✓Cleanest month: September; worst month: November.
Frequently asked questions
What is the air quality like in Honolulu in fall?▾
Across 2019–2025, the median daily AQI in Honolulu in fall was 26 (Good). 99.5% of days were Good, 0.5% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 637 monitored days in EPA's Air Quality System.
Is fall a good time for outdoor exercise in Honolulu?▾
A typical fall day in Honolulu sits in the Good range (median AQI 26), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Which pollutant causes Honolulu's fall air quality problems?▾
Ground-level ozone set the daily AQI on 61.1% of fall days in Honolulu. The highest fall AQI recorded in 2019–2025 was 55 (Moderate), in 2024.
Honolulu fall air quality, year by year
Honolulu fall air quality by year (Urban Honolulu, HI, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 91 | 25 | 0 | 42 | O3 |
| 2020 | 91 | 26 | 0 | 44 | PM2.5 |
| 2021cleanest | 91 | 23 | 0 | 49 | O3 |
| 2022 | 91 | 27 | 0 | 44 | O3 |
| 2023 | 91 | 27 | 0 | 55 | O3 |
| 2024worst | 91 | 27 | 0 | 49 | O3 |
| 2025 | 91 | 26 | 0 | 51 | O3 |
What fall air means in Honolulu
A typical fall day in Honolulu sits in the Good range (median AQI 26), so running, cycling and children's outdoor play are fine for everyone on most days; fewer than 1% of fall days reached AQI 101+ in 2019–2025.
Fall's median AQI of 26 is in line with Honolulu's whole-year median of 29, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median Fall AQI across every EPA metro area (296,275 metro-days, 2019–2025) is 40, so Honolulu runs below the national Fall norm; 0.0% of its Fall days topped AQI 100 versus 1.5% nationally (below average).
Within the season, September is the cleanest month (median AQI 22, 0.0% of days above 100) and November the worst (median 31, 0.0% above 100).
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 season 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.