Manchester Air Quality in December
Across 2019–2025, Manchester's December air quality had a median AQI of 33 (Good) over 217 monitored days in the Manchester-Nashua, NH area. 0.0% of December days (0 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 78.8% of days. The cleanest December on record here was 2023 (median AQI 25, 0 days above 100) and the worst was 2025 (median 36, 0 days above 100, peak AQI 47).
- Good: 97.2%
- Moderate: 2.8%
- Unhealthy for Sensitive Groups: 0.0%
- Unhealthy or worse: 0.0%
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How is the air in Manchester in December?
Good on a typical day: median AQI 33 across 2019–2025, with 0.0% of December days above AQI 100. Ground-level ozone is the main driver.
- ✓97.2% of December days were Good (AQI 0–50), 2.8% Moderate (51–100).
- ✓0 days of 217 reached AQI 101+; the December peak was 54.
- ✓Best December: 2023; worst December: 2025.
Frequently asked questions
What is the air quality like in Manchester in December?▾
Across 2019–2025, the median daily AQI in Manchester in December was 33 (Good). 97.2% of days were Good, 2.8% Moderate, and 0.0% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is December a good time for outdoor exercise in Manchester?▾
A typical December 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 December days reached AQI 101+ in 2019–2025.
Which pollutant causes Manchester's December air quality problems?▾
Ground-level ozone set the daily AQI on 78.8% of December days in Manchester. The highest December AQI recorded in 2019–2025 was 54 (Moderate), in 2025.
Manchester December air quality, year by year
Manchester December air quality by year (Manchester-Nashua, NH, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 35 | 0 | 53 | O3 |
| 2020 | 31 | 31 | 0 | 52 | O3 |
| 2021 | 31 | 33 | 0 | 47 | O3 |
| 2022 | 31 | 33 | 0 | 54 | O3 |
| 2023cleanest | 31 | 25 | 0 | 39 | PM2.5 |
| 2024 | 31 | 33 | 0 | 52 | O3 |
| 2025worst | 31 | 36 | 0 | 47 | O3 |
What December air means in Manchester
A typical December 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 December days reached AQI 101+ in 2019–2025.
December'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 December AQI across every EPA metro area (95,590 metro-days, 2019–2025) is 39, so Manchester runs below the national December norm; 0.0% of its December days topped AQI 100 versus 0.7% nationally (about the same).
December is part of Manchester's winter season (December, January, February); the winter 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.