Honolulu Air Quality in 2021
In 2021, Honolulu's air quality (Urban Honolulu, HI area) had a median daily AQI of 28 (Good) across 365 monitored days. 0 days (0.0%) reached Unhealthy for Sensitive Groups or worse, 364 were Good, and the year's peak AQI was 58 (Moderate). Ground-level ozone set the daily AQI on 266 of those days. The cleanest month of 2021 was October (median AQI 21, 0 days above 100) and the worst was December (median 38, 0 days above 100, peak 46).
- Good: 99.7%
- Moderate: 0.3%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How was Honolulu's air quality in 2021?
Good on a typical day: median AQI 28, with 0 days above AQI 100 out of 365 monitored — the 3rd cleanest of 7 years on record for the area.
- ✓Peak AQI in 2021: 58 (Moderate).
- ✓Ground-level ozone was the main pollutant on 266 days.
- ✓Cleanest month: October; worst: December.
Frequently asked questions
What was the average AQI in Honolulu in 2021?▾
EPA's Air Quality System puts Honolulu's (Urban Honolulu, HI) median daily AQI for 2021 at 28, which is Good. 0 days were Unhealthy for Sensitive Groups or worse and the year's highest AQI was 58.
Which month had the worst air quality in Honolulu in 2021?▾
The cleanest month of 2021 was October (median AQI 21, 0 days above 100) and the worst was December (median 38, 0 days above 100, peak 46).
Was 2021 a good or bad year for Honolulu's air?▾
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 3rd cleanest by days above AQI 100. 2021's median of 28 is in line with the area's typical annual median of 29.
Honolulu month by month in 2021
Honolulu air quality month by month, 2021 (Urban Honolulu, HI, EPA AQS daily AQI)
| Month | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| January | 31 | 31 | 0 | 43 | O3 |
| February | 28 | 34 | 0 | 43 | O3 |
| March | 31 | 34 | 0 | 47 | O3 |
| April | 30 | 34 | 0 | 41 | O3 |
| May | 31 | 28 | 0 | 33 | O3 |
| June | 30 | 22 | 0 | 30 | O3 |
| July | 31 | 22 | 0 | 58 | O3 |
| August | 31 | 23 | 0 | 43 | O3 |
| September | 30 | 22 | 0 | 47 | O3 |
| Octobercleanest | 31 | 21 | 0 | 37 | O3 |
| November | 30 | 27 | 0 | 49 | O3 |
| Decemberworst | 31 | 38 | 0 | 46 | O3 |
How 2021 compares
Among the 7 years EPA has published for the area (2019–2025), 2021 ranks 3rd cleanest by days above AQI 100.
2021's median of 28 is in line with the area's typical annual median of 29.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Honolulu
The latest EPA AirNow observation puts Honolulu's AQI at 21 (PM2.5). The figures above are multi-year annual 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.