SmogRank / United Kingdom / Northern Ireland / Derry

Derry, month by month

Derry has a measured daily mean on 761 days since 1 January 2023. Its worst month was January 2024, at 58 US AQI (12.6 µg/m³), 633rd of 2,385 cities on that month's world ranking. Its cleanest was September 2025, at 12 US AQI (2.2 µg/m³).

Every month since 2023

2026too few days for a mean (a year needs 199)88 days measured
Jan41#1,712Feb32#2,465Mar29#2,638AprnoneMaynoneJunnoneJulnoneAugnoneSep1 dayOct12#2,711
2025too few days for a mean (a year needs 256)223 days measured
JannoneFebnoneMar2 daysApr34#2,263May18#2,711Jun18#2,468Jul19#2,812Aug18#2,866Sep12#3,091Oct17#2,564Nov12 daysDec37#2,275
2024too few days for a mean (a year needs 257)229 days measured
Jan58#633Feb54#582Mar16 daysApr20 daysMay44#1,314Jun20 daysJul20 daysAug34#1,708Sep46#757Oct20 daysNovnoneDecnone
2023too few days for a mean (a year needs 256)221 days measured
Jan56#342Feb2 daysMar11 daysApr50#605May18 daysJun17 daysJul18 daysAug18 daysSep32#1,837Oct14 daysNov54#462Dec51#875
Each square is a month's mean PM2.5 in US AQI from Derry's measured days, with its place on that month's world ranking under it. A month has a mean once 70% of its days are measured, the rule the monthly rankings use; under that, the square gives the days measured. Each square opens that month's ranking with Derry marked; each year, the year's. A dashed square is the running month, so far.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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

24 months
MonthWhy
Sep 20261 of 30 days measured; a month needs 21. The others: 29 with under 18 hours of readings or readings that failed our checks.
Aug 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jul 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Jun 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
May 2026No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Apr 2026No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Nov 202512 of 30 days measured; a month needs 21. The others: 18 with under 18 hours of readings or readings that failed our checks.
Mar 20252 of 31 days measured; a month needs 22. The others: 29 with under 18 hours of readings or readings that failed our checks.
Feb 2025No day measured. The others: 28 with under 18 hours of readings or readings that failed our checks.
Jan 2025No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Dec 2024No day measured. The others: 31 with under 18 hours of readings or readings that failed our checks.
Nov 2024No day measured. The others: 30 with under 18 hours of readings or readings that failed our checks.
Oct 202420 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Jul 202420 of 31 days measured; a month needs 22. The others: 11 with under 18 hours of readings or readings that failed our checks.
Jun 202420 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Apr 202420 of 30 days measured; a month needs 21. The others: 10 with under 18 hours of readings or readings that failed our checks.
Mar 202416 of 31 days measured; a month needs 22. The others: 15 with under 18 hours of readings or readings that failed our checks.
Oct 202314 of 31 days measured; a month needs 22. The others: 17 with under 18 hours of readings or readings that failed our checks.
Aug 202318 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Jul 202318 of 31 days measured; a month needs 22. The others: 1 missing from OpenAQ's archive, 12 with under 18 hours of readings or readings that failed our checks.
Jun 202317 of 30 days measured; a month needs 21. The others: 13 with under 18 hours of readings or readings that failed our checks.
May 202318 of 31 days measured; a month needs 22. The others: 13 with under 18 hours of readings or readings that failed our checks.
Mar 202311 of 31 days measured; a month needs 22. The others: 20 missing from OpenAQ's archive.
Feb 20232 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive, 1 with under 18 hours of readings or readings that failed our checks.

A day counts once 18 hours of it are measured; a month needs 70% of its days.

Derry's worst months

MonthUS AQIDays measuredWorld rank
January 2024 5812.6 µg/m³27 of 31633rdof 2,385
January 2023 5612.0 µg/m³25 of 31342ndof 1,261
November 2023 5410.8 µg/m³28 of 30462ndof 2,243
February 2024 5410.7 µg/m³22 of 29582ndof 2,486
December 2023 519.3 µg/m³25 of 31875thof 2,247
April 2023 509.0 µg/m³21 of 30605thof 1,622

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.

Derry's worst days

DayUS AQI
8 Jan 2024 10537.2 µg/m³
4 Dec 2023 9834.4 µg/m³
29 Nov 2023 9231.0 µg/m³
7 Jan 2024 8728.6 µg/m³
31 Dec 2025 8024.8 µg/m³
2 Jan 2023 7722.9 µg/m³
1 Jan 2023 7722.8 µg/m³
1 Dec 2023 7622.6 µg/m³
11 Feb 2024 7622.6 µg/m³
3 Nov 2023 7522.0 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, Derry, United Kingdom, 1 Jan 2023 – 11 Oct 2026. Monitor data from UK-AIR (Defra), read from the publisher; sources listed at smogrank.com/sources. smogrank.com/gb/derry/history (accessed 12 Oct 2026).

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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.

Derry now: the last 24 hours, its ranks today and the last 12 months day by day.

Updated 2026-10-12 18:07 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).