2025 Ozone Exceedances
(Through August 13, 2025)
Below are the exceedances of the 0.070 parts per million (ppm) eight-hour average ozone standard, and the dates they occurred for each ozone monitor in New England. These data are preliminary, not quality assured and are subject to change.
On this page:
Connecticut
| Monitor Location | Concentration (ppm) | Date/AQI Map |
|---|---|---|
| Abington | 0.073 | August 12, 2025 Peak Ozone AQI Map |
| Cornwall | 0.071 | |
| Danbury | 0.085 | |
| East Hartford | 0.091 | |
| Greenwich | 0.076 | |
| Middletown | 0.084 | |
| Stafford | 0.075 | |
| Westport | 0.075 | |
| Danbury | 0.079 | August 11, 2025 Peak Ozone AQI Map |
| East Harford | 0.075 | |
| Groton | 0.079 | |
| Madison | 0.075 | |
| Middletown | 0.081 | |
| New Haven | 0.076 | |
| Stratford | 0.082 | |
| Westport | 0.081 | |
| Greenwich | 0.074 | August 10, 2025 Peak Ozone AQI Map |
| Stratford | 0.075 | |
| Westport | 0.080 | |
| Madison | 0.079 | August 4, 2025 Peak Ozone AQI Map |
| Stratford | 0.072 | |
| Westport | 0.082 | |
| Greenwich | 0.094 | July 29, 2025 Peak Ozone AQI Map |
| Groton | 0.076 | |
| Madison | 0.089 | |
| Stratford | 0.092 | |
| Westport | 0.095 | |
| Greenwich | 0.075 | July 25, 2025 Peak Ozone AQI Map |
| Groton | 0.071 | |
| Madison | 0.074 | |
| Stratford | 0.084 | |
| Westport | 0.075 | |
| Danbury | 0.075 | July 16, 2025 Peak Ozone AQI Map |
| Greenwich | 0.073 | July 8, 2025 Peak Ozone AQI Map |
| Groton | 0.072 | |
| Stratford | 0.075 | |
| Westport | 0.072 | |
| Danbury | 0.073 | July 6, 2025 Peak Ozone AQI Map |
| Madison | 0.074 | |
| Middletown | 0.076 | |
| New Haven | 0.076 | |
| Stafford | 0.073 | |
| Stratford | 0.072 | |
| Westport | 0.072 | |
| Middletown | 0.072 | July 1, 2025 Peak Ozone AQI Map |
| Stratford | 0.076 | |
| Westport | 0.072 | |
| Madison | 0.077 | June 25, 2025 Peak Ozone AQI Map |
| Stratford | 0.075 | |
| Groton | 0.072 | June 24, 2025 Peak Ozone AQI Map |
| Madison | 0.084 | |
| Stratford | 0.079 | |
| Westport | 0.071 | |
| Greenwich | 0.076 | June 23, 2025 Peak Ozone AQI Map |
| Greenwich | 0.072 | June 12, 2025 Peak Ozone AQI Map |
| Groton | 0.081 | |
| Madison | 0.086 | |
| Stratford | 0.080 | |
| Westport | 0.071 | |
| Groton | 0.073 | June 11, 2025 Peak Ozone AQI Map |
| Madison | 0.072 | |
| Stratford | 0.073 | |
| Westport | 0.072 | |
| Danbury | 0.076 | June 6, 2025 Peak Ozone AQI Map |
| East Hartford | 0.072 | |
| Cornwall | 0.090 | June 5, 2025 Peak Ozone AQI Map |
| Danbury | 0.092 | |
| East Hartford | 0.091 | |
| Greenwich | 0.076 | |
| Groton | 0.079 | |
| Madison | 0.079 | |
| Middletown | 0.086 | |
| Stafford | 0.081 | |
| Stratford | 0.083 | |
| Westport | 0.090 | |
| Cornwall | 0.082 | June 4, 2025 Peak Ozone AQI Map |
| Danbury | 0.081 | |
| East Hartford | 0.075 | |
| Stafford | 0.073 | |
| Middletown | 0.071 | May 12, 2025 Peak Ozone AQI Map |
| Cornwall | 0.072 | April 25, 2025 Peak Ozone AQI Map |
| Cornwall | 0.076 | April 24, 2025 Peak Ozone AQI Map |
| Danbury | 0.071 | |
| East Hartford | 0.071 | |
| Stafford | 0.071 |
Maine
| Monitor Location | Concentration (ppm) | Date/AQI Map |
|---|---|---|
| Acadia NP | 0.072 | August 13, 2025 Peak Ozone AQI Map |
| Bar Harbor | 0.080 | |
| Holden | 0.075 | |
| Acadia NP | 0.075 | August 12, 2025 Peak Ozone AQI Map |
| Bar Harbor | 0.075 | |
| Cape Elizabeth | 0.081 | |
| Holden | 0.075 | |
| Kennebunkport | 0.093 | |
| Popham Beach SP | 0.073 | |
| Portland | 0.077 | |
| Portland | 0.077 | August 11, 2025 Peak Ozone AQI Map |
| Bar Harbor | 0.071 | June 5, 2025 Peak Ozone AQI Map |
| Cape Elizabeth | 0.078 | |
| Kennebunkport | 0.084 | |
| Portland | 0.072 | |
| Bar Harbor | 0.077 | June 4, 2025 Peak Ozone AQI Map |
Massachusetts
| Monitor Location | Concentration (ppm) | Date/AQI Map |
|---|---|---|
| Chelmsford | 0.072 | August 12, 2025 Peak Ozone AQI Map |
| Chicopee | 0.072 | |
| E. Milton-Blue Hill | 0.072 | |
| Haverhill | 0.080 | |
| Lynn | 0.081 | |
| Truro | 0.079 | |
| Fall River | 0.073 | August 11, 2025 Peak Ozone AQI Map |
| Lynn | 0.073 | |
| Martha's Vineyard | 0.086 | June 24, 2025 Peak Ozone AQI Map |
| Fairhaven | 0.072 | June 12, 2025 Peak Ozone AQI Map |
| Martha's Vineyard | 0.076 | |
| Truro | 0.072 | |
| Brockton | 0.073 | June 5, 2025 Peak Ozone AQI Map |
| Chicopee | 0.075 | |
| East Milton-Blue Hill | 0.072 | |
| Fall River | 0.076 | |
| Lynn | 0.080 | |
| Truro | 0.074 | |
| Ware | 0.071 | |
| Weymouth | 0.078 | |
| Chicopee | 0.073 | June 4, 2025 Peak Ozone AQI Map |
| Greenfield | 0.071 | |
| Pittsfield | 0.075 | |
| Ware | 0.071 |
New Hampshire
| Monitor Location | Concentration (ppm) | Date/AQI Map |
|---|---|---|
| Odiorne SP | 0.085 | August 12, 2025 Peak Ozone AQI Map |
| Portsmouth | 0.082 | |
| Summit | 0.071 | June 29, 2025 Peak Ozone AQI Map |
| Odiorne State | 0.074 | June 5, 2025 Peak Ozone AQI Map |
| Portsmouth | 0.075 | |
| Miller State Park | 0.071 | June 4, 2025 Peak Ozone AQI Map |
| Summit | 0.075 | March 15, 2025 Peak Ozone AQI Map |
Rhode Island
| Monitor Location | Concentration (ppm) | Date/AQI Map |
|---|---|---|
| Narragansett | 0.077 | August 11, 2025 Peak Ozone AQI Map |
| East Matunuck | 0.072 | June 24, 2025 Peak Ozone AQI Map |
| East Matunuck | 0.075 | June 12, 2025 Peak Ozone AQI Map |
| Narragansett | 0.079 | |
| Narragansett | 0.074 | June 5, 2025 Peak Ozone AQI Map |
Vermont
| Monitor Location | Concentration (ppm) | Date/AQI Map |
|---|---|---|
| Underhill | 0.073 | March 15, 2025 Peak Ozone AQI Map |