SmogRank / Portugal / Leiria / Vieira de Leiria

Vieira de Leiria, month by month

Vieira de Leiria has a measured daily mean on 345 days since 1 January 2023. Its worst month was February 2024, at 60 US AQI (13.8 µg/m³), 380th of 2,486 cities on that month's world ranking. Its cleanest was September 2023, at 29 US AQI (5.3 µg/m³).

Every month since 2023

2026too few days for a mean (a year needs 199)5 days measured
Jan4 daysFeb1 dayMarnoneAprnoneMaynoneJunnoneJulnoneAugnoneSepnoneOctnone
2025too few days for a mean (a year needs 256)4 days measured
JannoneFebnoneMar1 dayAprnoneMaynoneJunnoneJul1 dayAugnoneSep1 dayOctnoneNovnoneDec1 day
2024too few days for a mean (a year needs 257)81 days measured
Jan56#717Feb60#380Mar11 daysApr1 dayMay2 daysJun2 daysJul2 daysAug1 daySepnoneOct4 daysNov2 daysDecnone
2023too few days for a mean (a year needs 256)255 days measured
Jan7 daysFeb3 daysMar7 daysApr36#1,132May42#1,042Jun44#1,123Jul52#714Aug21 daysSep29#1,938Oct53#326Nov53#619Dec57#420
Each square is a month's mean PM2.5 in US AQI from Vieira de Leiria'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 Vieira de Leiria marked; each year, the year's.
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

36 months
MonthWhy
Oct 2026No day measured. The others: 10 with no readings from the monitor, 1 with under 18 hours of readings or readings that failed our checks.
Sep 2026No day measured. The others: 7 with no readings from the monitor, 6 with readings for part of the day (a day needs 18 hours), 17 with readings left out by our checks.
Aug 2026No day measured. The others: 3 with no readings from the monitor, 6 with readings for part of the day (a day needs 18 hours), 22 with readings left out by our checks.
Jul 2026No day measured. The others: 15 with readings for part of the day (a day needs 18 hours), 15 with readings left out by our checks, 1 with under 18 hours of readings or readings that failed our checks.
Jun 2026No day measured. The others: 13 with readings for part of the day (a day needs 18 hours), 17 with readings left out by our checks.
May 2026No day measured. The others: 1 with no readings from the monitor, 11 with readings for part of the day (a day needs 18 hours), 18 with readings left out by our checks, 1 with under 18 hours of readings or readings that failed our checks.
Apr 2026No day measured. The others: 6 with readings for part of the day (a day needs 18 hours), 24 with readings left out by our checks.
Mar 2026No day measured. The others: 8 with readings for part of the day (a day needs 18 hours), 23 with readings left out by our checks.
Feb 20261 of 28 days measured; a month needs 20. The others: 11 with no readings from the monitor, 11 with readings for part of the day (a day needs 18 hours), 5 with readings left out by our checks.
Jan 20264 of 31 days measured; a month needs 22. The others: 3 with no readings from the monitor, 12 with readings for part of the day (a day needs 18 hours), 12 with readings left out by our checks.
Dec 20251 of 31 days measured; a month needs 22. The others: 4 with no readings from the monitor, 10 with readings for part of the day (a day needs 18 hours), 16 with readings left out by our checks.
Nov 2025No day measured. The others: 11 with readings for part of the day (a day needs 18 hours), 19 with readings left out by our checks.
Oct 2025No day measured. The others: 13 with readings for part of the day (a day needs 18 hours), 18 with readings left out by our checks.
Sep 20251 of 30 days measured; a month needs 21. The others: 6 with readings for part of the day (a day needs 18 hours), 23 with readings left out by our checks.
Aug 2025No day measured. The others: 3 with readings for part of the day (a day needs 18 hours), 28 with readings left out by our checks.
Jul 20251 of 31 days measured; a month needs 22. The others: 7 with readings for part of the day (a day needs 18 hours), 23 with readings left out by our checks.
Jun 2025No day measured. The others: 12 with readings for part of the day (a day needs 18 hours), 18 with readings left out by our checks.
May 2025No day measured. The others: 1 with no readings from the monitor, 9 with readings for part of the day (a day needs 18 hours), 21 with readings left out by our checks.
Apr 2025No day measured. The others: 7 with readings for part of the day (a day needs 18 hours), 23 with readings left out by our checks.
Mar 20251 of 31 days measured; a month needs 22. The others: 1 with no readings from the monitor, 9 with readings for part of the day (a day needs 18 hours), 20 with readings left out by our checks.
Feb 2025No day measured. The others: 5 with readings for part of the day (a day needs 18 hours), 23 with readings left out by our checks.
Jan 2025No day measured. The others: 5 with readings for part of the day (a day needs 18 hours), 26 with readings left out by our checks.
Dec 2024No day measured. The others: 8 with readings for part of the day (a day needs 18 hours), 23 with readings left out by our checks.
Nov 20242 of 30 days measured; a month needs 21. The others: 4 with readings for part of the day (a day needs 18 hours), 24 with readings left out by our checks.
Oct 20244 of 31 days measured; a month needs 22. The others: 16 with readings for part of the day (a day needs 18 hours), 11 with readings left out by our checks.
Sep 2024No day measured. The others: 30 with readings for part of the day (a day needs 18 hours).
Aug 20241 of 31 days measured; a month needs 22. The others: 3 with no readings from the monitor, 14 with readings for part of the day (a day needs 18 hours), 13 with readings left out by our checks.
Jul 20242 of 31 days measured; a month needs 22. The others: 8 with readings for part of the day (a day needs 18 hours), 21 with readings left out by our checks.
Jun 20242 of 30 days measured; a month needs 21. The others: 1 with readings for part of the day (a day needs 18 hours), 27 with readings left out by our checks.
May 20242 of 31 days measured; a month needs 22. The others: 29 with readings left out by our checks.
Apr 20241 of 30 days measured; a month needs 21. The others: 5 with readings for part of the day (a day needs 18 hours), 24 with readings left out by our checks.
Mar 202411 of 31 days measured; a month needs 22. The others: 10 with no readings from the monitor, 6 with readings for part of the day (a day needs 18 hours), 4 with readings left out by our checks.
Aug 202321 of 31 days measured; a month needs 22. The others: 1 with no readings from the monitor, 7 with readings for part of the day (a day needs 18 hours), 2 with readings left out by our checks.
Mar 20237 of 31 days measured; a month needs 22. The others: 2 with no readings from the monitor, 2 with readings for part of the day (a day needs 18 hours), 20 missing from OpenAQ's archive.
Feb 20233 of 28 days measured; a month needs 20. The others: 25 missing from OpenAQ's archive.
Jan 20237 of 31 days measured; a month needs 22. The others: 3 with no readings from the monitor, 14 with readings for part of the day (a day needs 18 hours), 7 missing from OpenAQ's archive.

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

Vieira de Leiria's worst months

MonthUS AQIDays measuredWorld rankEpisode
February 2024 6013.8 µg/m³25 of 29380thof 2,486Southern Europe, February 2024
Spain, Portugal and France, February 2024
December 2023 5712.2 µg/m³31 of 31420thof 2,247–
January 2024 5611.8 µg/m³31 of 31717thof 2,385–
October 2023 5310.2 µg/m³23 of 31326thof 2,012–
November 2023 5310.0 µg/m³29 of 30619thof 2,243–
July 2023 529.5 µg/m³25 of 31714thof 1,432–

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.

Vieira de Leiria's worst days

DayUS AQIEpisode
29 Jul 2023 17184.1 µg/m³–
5 Feb 2024 10135.6 µg/m³Southern Europe, February 2024
6 Feb 2024 9432.2 µg/m³Southern Europe, February 2024
2 Feb 2024 9130.5 µg/m³Spain, Portugal and France, February 2024
6 Jan 2023 9030.3 µg/m³–
4 Feb 2024 8527.6 µg/m³Southern Europe, February 2024
25 Dec 2023 8426.9 µg/m³–
7 Feb 2024 8326.3 µg/m³Southern Europe, February 2024
26 Nov 2023 8225.8 µg/m³–
25 Nov 2023 7923.9 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, Vieira de Leiria, Portugal, 1 Jan 2023 – 23 Feb 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/pt/vieira-de-leiria/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.

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

Updated 2026-10-12 20:07 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).