Honolulu Best & Worst AQI Days: Air Quality Guide
The worst air quality day on record for Honolulu (Urban Honolulu, HI area) was January 1, 2023, when the daily AQI reached 117 (Unhealthy for Sensitive Groups), set by fine particulate matter (PM2.5). Across 2,557 monitored days in 2019–2025, 0 of the 10 worst days were Unhealthy (AQI 151+) or worse; 10 of the 10 were driven by fine particulate matter (PM2.5), and 6 of them fell in 2023. The cleanest day was July 15, 2019 at AQI 9 (Good); the 10 best days span 6 different years.
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When were Honolulu's worst and best air quality days?
Worst: January 1, 2023, AQI 117 (Unhealthy for Sensitive Groups, PM2.5). Best: July 15, 2019, AQI 9 (Good). Based on 2,557 EPA-monitored days in the Urban Honolulu, HI area, 2019–2025.
- ✓0 of the 10 worst days were Unhealthy (AQI 151+) or worse; the 10th-worst was AQI 59 (Moderate).
- ✓Fine particulate matter (PM2.5) drove 10 of the 10 worst days.
- ✓2023 accounts for 6 of the 10 worst days.
Frequently asked questions
What was the worst air quality day in Honolulu?▾
January 1, 2023: the Urban Honolulu, HI area's daily AQI hit 117 (Unhealthy for Sensitive Groups), driven by fine particulate matter (PM2.5). That is the highest of 2,557 monitored days in 2019–2025.
What was the best air quality day in Honolulu?▾
July 15, 2019, with a daily AQI of 9 (Good). The daily AQI is the highest reading from any monitor in the area, so even the cleanest day reflects the area's worst monitor.
What was Honolulu's worst air quality day in 2025?▾
April 4, 2025, AQI 59 (Moderate), set by fine particulate matter (PM2.5).
Which pollutant causes Honolulu's worst air days?▾
Fine particulate matter (PM2.5) set the AQI on 10 of the 10 worst days. The tables above list the defining pollutant for every day.
Honolulu's 10 worst air quality days, 2019–2025
Highest daily AQI recorded for the Urban Honolulu, HI area (EPA AQS). The daily AQI is the highest reading from any monitor in the area that day.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2023 page) | 117 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2024 page) | 85 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 3 | (2023 page) | 73 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2023 page) | 66 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 5 | (2023 page) | 64 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 6 | (2020 page) | 63 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 7 | (2023 page) | 62 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 8 | (2019 page) | 62 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 9 | (2023 page) | 60 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
| 10 | (2025 page) | 59 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
Worst day of each year in Honolulu
The single highest-AQI day in each year on record. Click a year for its full month-by-month statistics.
| Year | Worst day | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 2019 | 62 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2020 | 63 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2021 | 58 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2022 | 57 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2023 | 117 | Unhealthy for Sensitive Groups | PM2.5 — fine particulate matter (PM2.5) | |
| 2024 | 85 | Moderate | PM2.5 — fine particulate matter (PM2.5) | |
| 2025 | 59 | Moderate | PM2.5 — fine particulate matter (PM2.5) |
Honolulu's 10 best air quality days, 2019–2025
Lowest daily AQI recorded for the Urban Honolulu, HI area. Ties are listed most recent first.
| # | Date | AQI | Category | Defining pollutant |
|---|---|---|---|---|
| 1 | (2019 page) | 9 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 2 | (2021 page) | 11 | Good | PM10 — coarse dust (PM10) |
| 3 | (2021 page) | 11 | Good | PM2.5 — fine particulate matter (PM2.5) |
| 4 | (2021 page) | 11 | Good | O3 — ground-level ozone |
| 5 | (2020 page) | 12 | Good | O3 — ground-level ozone, in peak ozone season |
| 6 | (2019 page) | 12 | Good | NO2 — nitrogen dioxide |
| 7 | (2019 page) | 12 | Good | O3 — ground-level ozone, in peak ozone season |
| 8 | (2025 page) | 13 | Good | O3 — ground-level ozone, in peak ozone season |
| 9 | (2023 page) | 13 | Good | O3 — ground-level ozone |
| 10 | (2022 page) | 13 | Good | O3 — ground-level ozone |
Right now in Honolulu
The latest EPA AirNow observation puts Honolulu's AQI at 15 (PM2.5). The days above are historical records, 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.