Manchester Air Quality in September
Across 2019–2025, Manchester's September air quality had a median AQI of 33 (Good) over 210 monitored days in the Manchester-Nashua, NH area. 0.5% of September days (1 of 210) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 89.0% of days. The cleanest September on record here was 2019 (median AQI 30, 0 days above 100) and the worst was 2023 (median 39, 1 day above 100, peak AQI 119).
- Good: 91.9%
- Moderate: 7.6%
- Unhealthy for Sensitive Groups: 0.5%
- Unhealthy or worse: 0.0%
Improve Indoor Air Quality
Even with good outdoor air in Manchester, indoor PM2.5, dust and allergens build up. A True-HEPA purifier keeps a bedroom or office consistently clean.
Recommended: Levoit Core 400S — True HEPA · CADR ~141 CFM · rooms up to 219 sq ft
As an Amazon Associate, we earn from qualifying purchases.
How is the air in Manchester in September?
Good on a typical day: median AQI 33 across 2019–2025, with 0.5% of September days above AQI 100. Ground-level ozone is the main driver.
- ✓91.9% of September days were Good (AQI 0–50), 7.6% Moderate (51–100).
- ✓1 day of 210 reached AQI 101+; the September peak was 119.
- ✓Best September: 2019; worst September: 2023.
Frequently asked questions
What is the air quality like in Manchester in September?▾
Across 2019–2025, the median daily AQI in Manchester in September was 33 (Good). 91.9% of days were Good, 7.6% Moderate, and 0.5% 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 Manchester?▾
A typical September day in Manchester sits in the Good range (median AQI 33), 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 Manchester's September air quality problems?▾
Ground-level ozone set the daily AQI on 89.0% of September days in Manchester. The highest September AQI recorded in 2019–2025 was 119 (Unhealthy for Sensitive Groups), in 2023.
Manchester September air quality, year by year
Manchester September air quality by year (Manchester-Nashua, NH, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019cleanest | 30 | 30 | 0 | 74 | O3 |
| 2020 | 30 | 31 | 0 | 64 | O3 |
| 2021 | 30 | 35 | 0 | 48 | O3 |
| 2022 | 30 | 31 | 0 | 43 | O3 |
| 2023worst | 30 | 39 | 1 | 119 | O3 |
| 2024 | 30 | 34 | 0 | 84 | O3 |
| 2025 | 30 | 36 | 0 | 58 | O3 |
What September air means in Manchester
A typical September day in Manchester sits in the Good range (median AQI 33), 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 33 is below Manchester's whole-year median of 37, 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 Manchester runs below the national September norm; 0.5% of its September days topped AQI 100 versus 2.7% nationally (below average).
September is part of Manchester's fall season (September, October, November); the fall page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Manchester
The latest EPA AirNow observation puts Manchester's AQI at 24 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Manchester air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Manchester-Nashua, NH), 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.