Hartford Air Quality in May
Across 2019–2025, Hartford's May air quality had a median AQI of 43 (Good) over 217 monitored days in the Hartford-West Hartford-East Hartford, CT area. 1.4% of May days (3 of 217) reached Unhealthy for Sensitive Groups or worse, and ground-level ozone set the daily AQI on 84.8% of days. The cleanest May on record here was 2020 (median AQI 41, 0 days above 100) and the worst was 2025 (median 40, 1 day above 100, peak AQI 101).
- Good: 78.3%
- Moderate: 20.3%
- Unhealthy for Sensitive Groups: 1.4%
- Unhealthy or worse: 0.0%
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How is the air in Hartford in May?
Good on a typical day: median AQI 43 across 2019–2025, with 1.4% of May days above AQI 100. Ground-level ozone is the main driver.
- ✓78.3% of May days were Good (AQI 0–50), 20.3% Moderate (51–100).
- ✓3 days of 217 reached AQI 101+; the May peak was 119.
- ✓Best May: 2020; worst May: 2025.
Frequently asked questions
What is the air quality like in Hartford in May?▾
Across 2019–2025, the median daily AQI in Hartford in May was 43 (Good). 78.3% of days were Good, 20.3% Moderate, and 1.4% reached Unhealthy for Sensitive Groups or worse, based on 217 monitored days in EPA's Air Quality System.
Is May a good time for outdoor exercise in Hartford?▾
A typical May day in Hartford sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 71 of May days (1.4%) reached AQI 101+ in 2019–2025.
Which pollutant causes Hartford's May air quality problems?▾
Ground-level ozone set the daily AQI on 84.8% of May days in Hartford. The highest May AQI recorded in 2019–2025 was 119 (Unhealthy for Sensitive Groups), in 2025.
Hartford May air quality, year by year
Hartford May air quality by year (Hartford-West Hartford-East Hartford, CT, EPA AQS daily AQI)
| Year | Days monitored | Median AQI | Days above 100 | Peak AQI | Main pollutant |
|---|---|---|---|---|---|
| 2019 | 31 | 44 | 0 | 67 | O3 |
| 2020cleanest | 31 | 41 | 0 | 84 | O3 |
| 2021 | 31 | 40 | 1 | 101 | O3 |
| 2022 | 31 | 43 | 0 | 87 | O3 |
| 2023 | 31 | 46 | 0 | 100 | O3 |
| 2024 | 31 | 40 | 1 | 119 | O3 |
| 2025worst | 31 | 40 | 1 | 101 | O3 |
What May air means in Hartford
A typical May day in Hartford sits in the Good range (median AQI 43), so running, cycling and children's outdoor play are fine for everyone on most days; about 1 day in 71 of May days (1.4%) reached AQI 101+ in 2019–2025.
May's median AQI of 43 is in line with Hartford's whole-year median of 43, so this period is neither a clean nor a dirty stretch for the area. Nationally, the median May AQI across every EPA metro area (104,064 metro-days, 2019–2025) is 44, so Hartford runs in line with the national May norm; 1.4% of its May days topped AQI 100 versus 1.3% nationally (about the same).
May is part of Hartford's spring season (March, April, May); the spring page pools all three months.
Activity-specific thresholds: running, cycling, kids' sports.
Right now in Hartford
The latest EPA AirNow observation puts Hartford's AQI at 36 (PM2.5). The figures above are multi-year month statistics, not today's reading.
View current Hartford air quality →Source: EPA Air Quality System (AQS) pre-generated Daily AQI by CBSA files — daily AQI by CBSA (Hartford-West Hartford-East Hartford, CT), 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.