SmogRank / United States / Vermont / Hartford
Hartford, month by month
Hartford, Vermont has a measured daily mean on 1,273 days since 1 January 2023. Its worst month was August 2025, at 55 US AQI (11.4 µg/m³), 909th of 2,901 cities on that month's world ranking. Its cleanest was April 2024, at 16 US AQI (2.8 µg/m³). 2025 averaged 34 US AQI (6.1 µg/m³), against 26 US AQI (4.7 µg/m³) in 2024.
Every month since 2023
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Months without a mean, and why
5 months
| Month | Why |
|---|---|
| Sep 2025 | 13 of 30 days measured; a month needs 21. The others: 13 with no readings from the monitor, 4 with readings for part of the day (a day needs 18 hours). |
| Nov 2023 | 19 of 30 days measured; a month needs 21. The others: 9 with no readings from the monitor, 2 with readings for part of the day (a day needs 18 hours). |
| Mar 2023 | 11 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive. |
| Feb 2023 | 3 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive. |
| Jan 2023 | 17 of 31 days measured; a month needs 22. The others: 7 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours), 6 missing from OpenAQ's archive. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Hartford's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| August 2025 | 5511.4 µg/m³ | 909thof 2,901 | North-eastern United States and Canada, 29 July to 9 August 2025 |
| July 2023 | 5310.4 µg/m³ | 619thof 1,432 | United States and Canada, July 2023 Eastern United States and Canada, June and July 2023 |
| July 2025 | 5310.1 µg/m³ | 1,244thof 2,889 | North-eastern United States and Canada, 29 July to 9 August 2025 North-eastern United States and Canada, 24 to 28 July 2025 |
| June 2025 | 5310.0 µg/m³ | 1,296thof 2,508 | Northern United States and Canada, May and June 2025 |
| July 2026 | 509.0 µg/m³ | 1,604thof 2,784 | – |
| August 2024 | 427.5 µg/m³ | 1,399thof 2,010 | – |
Monthly means over the days measured; finished months only. World rank: its place on that month's world ranking of every city with enough days. Each month opens that ranking.
Hartford's worst days
Daily means, the highest since 1 Jan 2023; the WHO's daily guideline is 15 µg/m³. Each date opens that day's world ranking, and each episode the bad-air spell it was part of.
Use this history
SmogRank, PM2.5 monthly and daily means, Hartford, Vermont, United States, 1 Jan 2023 – 11 Oct 2026. Monitor data from AirNow, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/us/hartford-vermont/history (accessed 13 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Hartford now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-13 02:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some low-cost readings: Sensor.Community, ODbL (data and licence). Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); RMCAB (Secretaría Distrital de Ambiente, Bogotá); Love My Air (City and County of Denver), no reuse terms published (why we use them).