SmogRank / United Kingdom / Wales / Chepstow
Chepstow, month by month
Chepstow has a measured daily mean on 761 days since 1 January 2023. Its worst month was March 2026, at 57 US AQI (12.4 µg/m³), 1,143rd of 2,971 cities on that month's world ranking. Its cleanest was July 2025, at 24 US AQI (4.4 µg/m³).
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
23 months
| Month | Why |
|---|---|
| Sep 2026 | No day measured. The others: 30 with no readings from the monitor. |
| Aug 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Jul 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Jun 2026 | No day measured. The others: 30 with no readings from the monitor. |
| May 2026 | No day measured. The others: 31 with no readings from the monitor. |
| Apr 2026 | No day measured. The others: 30 with no readings from the monitor. |
| Nov 2025 | 12 of 30 days measured; a month needs 21. The others: 17 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours). |
| Oct 2025 | 21 of 31 days measured; a month needs 22. The others: 5 with no readings from the monitor, 3 with readings for part of the day (a day needs 18 hours), 2 with readings left out by our checks. |
| Mar 2025 | 2 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks. |
| Feb 2025 | No day measured. The others: 28 with under 18 hours of readings or readings that failed our checks. |
| Jan 2025 | No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks. |
| Dec 2024 | No day measured. The others: 31 with no readings from the monitor. |
| Nov 2024 | No day measured. The others: 30 with no readings from the monitor. |
| Apr 2024 | 18 of 30 days measured; a month needs 21. The others: 9 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours), 2 with readings left out by our checks. |
| Mar 2024 | 17 of 31 days measured; a month needs 22. The others: 5 with no readings from the monitor, 8 with readings for part of the day (a day needs 18 hours), 1 with readings left out by our checks. |
| Oct 2023 | 15 of 31 days measured; a month needs 22. The others: 3 with no readings from the monitor, 13 with readings for part of the day (a day needs 18 hours). |
| Aug 2023 | 21 of 31 days measured; a month needs 22. The others: 5 with no readings from the monitor, 2 with readings for part of the day (a day needs 18 hours), 3 with readings left out by our checks. |
| Jul 2023 | 15 of 31 days measured; a month needs 22. The others: 4 with no readings from the monitor, 11 with readings for part of the day (a day needs 18 hours), 1 missing from OpenAQ's archive. |
| Jun 2023 | 16 of 30 days measured; a month needs 21. The others: 2 with no readings from the monitor, 11 with readings for part of the day (a day needs 18 hours), 1 with readings left out by our checks. |
| May 2023 | 18 of 31 days measured; a month needs 22. The others: 1 with no readings from the monitor, 12 with readings for part of the day (a day needs 18 hours). |
| Mar 2023 | 9 of 31 days measured; a month needs 22. The others: 2 with readings left out by our checks, 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 | 18 of 31 days measured; a month needs 22. The others: 5 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours), 1 with readings left out by our checks, 6 missing from OpenAQ's archive. |
A day counts once 18 hours of it are measured; a month needs 70% of its days.
Chepstow's worst months
| Month | US AQI | World rank | Episode |
|---|---|---|---|
| March 2026 | 5712.4 µg/m³ | 1,143rdof 2,971 | Europe, 1 to 12 March 2026 |
| April 2023 | 5310.2 µg/m³ | 419thof 1,622 | – |
| April 2025 | 519.3 µg/m³ | 1,386thof 2,951 | – |
| December 2025 | 478.5 µg/m³ | 1,708thof 3,006 | – |
| May 2024 | 448.0 µg/m³ | 1,314thof 2,684 | – |
| January 2026 | 448.0 µg/m³ | 1,495thof 2,617 | – |
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.
Chepstow's worst days
| Day | US AQI | Episode |
|---|---|---|
| 9 Mar 2026 | 9633.2 µg/m³ | Europe, 1 to 12 March 2026 |
| 14 Feb 2023 | 8929.5 µg/m³ | Europe, 6 to 25 February 2023 |
| 15 Feb 2023 | 8426.6 µg/m³ | Europe, 6 to 25 February 2023 |
| 5 Mar 2026 | 8024.5 µg/m³ | Europe, 1 to 12 March 2026 |
| 25 Jan 2023 | 7522.0 µg/m³ | – |
| 20 Mar 2026 | 7522.0 µg/m³ | – |
| 8 Mar 2026 | 7521.8 µg/m³ | Europe, 1 to 12 March 2026 |
| 1 Jun 2024 | 7120.0 µg/m³ | – |
| 2 Dec 2023 | 7119.7 µg/m³ | – |
| 20 Sept 2024 | 7019.5 µg/m³ | – |
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, Chepstow, United Kingdom, 1 Jan 2023 – 12 Oct 2026. Monitor data from UK-AIR (Defra), read from the publisher; sources listed at smogrank.com/sources. smogrank.com/gb/chepstow/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.
Chepstow now: the last 24 hours, its ranks today and the last 12 months day by day.
Updated 2026-10-13 00:07 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).