SmogRank / Portugal / Azores / Angra do Heroísmo

Angra do Heroísmo, month by month

Angra do Heroísmo has a measured daily mean on 672 days since 17 October 2024. Its worst month was March 2026, at 19 US AQI (3.5 µg/m³), 3,185th of 3,285 cities on that month's world ranking. Its cleanest was December 2025, at 8 US AQI (1.5 µg/m³).

Every month since 2024

202616 so far271 days measured3,210th of 3,214 in the world

Jan19 daysFeb18#3,111 Mar19#3,185 Apr14#3,277 May15#3,205 Jun14#3,191 Jul17#3,005 Aug18#3,185 Sep13#3,326 Oct14#3,185

202513 for the year363 days measured2,925th of 2,926 in the world

Jan18#2,715 Feb12#2,843 Mar12#3,090 Apr13#3,136 May12#3,115 Jun14#3,100 Jul14#3,053 Aug18#3,060 Sep11#3,239 Oct10#3,008 Nov12#2,926 Dec8#3,196

2024too few days for a mean (a year needs 257)38 days measured

JanFebMarAprMayJunJulAugSepOct9 daysNov13 daysDec16 days

Each square is a month's mean PM2.5 in US AQI from Angra do Heroísmo'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 Angra do Heroísmo marked; each year, the year's. A dashed square is the running month, so far.

Good0–50

Moderate51–100

Unhealthy for 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

4 months

Month	Why
Jan 2026	19 of 31 days measured; a month needs 22. The others: 11 with no readings from the monitor, 1 with readings for part of the day (a day needs 18 hours).
Dec 2024	16 of 31 days measured; a month needs 22. The others: 15 with readings for part of the day (a day needs 18 hours).
Nov 2024	13 of 30 days measured; a month needs 21. The others: 17 with readings for part of the day (a day needs 18 hours).
Oct 2024	9 of 31 days measured; a month needs 22. The others: 6 with readings for part of the day (a day needs 18 hours).

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

Angra do Heroísmo's worst months

Month	US AQI	Days measured	World rank
March 2026	193.5 µg/m³	31 of 31	3,185thof 3,285
February 2026	183.3 µg/m³	28 of 28	3,111thof 3,180
August 2026	183.3 µg/m³	30 of 31	3,185thof 3,210
January 2025	183.2 µg/m³	31 of 31	2,715thof 2,754
August 2025	183.2 µg/m³	31 of 31	3,060thof 3,095
July 2026	173.1 µg/m³	31 of 31	3,005thof 3,035

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.

Angra do Heroísmo's worst days

Day	US AQI
21 Feb 2026	7521.8 µg/m³
14 Aug 2025	6013.7 µg/m³
20 Feb 2026	5712.5 µg/m³
1 Jun 2025	5410.6 µg/m³
21 Jul 2025	529.9 µg/m³
12 Aug 2025	529.5 µg/m³
13 Aug 2025	529.4 µg/m³
20 Mar 2026	519.1 µg/m³
15 Aug 2025	478.5 µg/m³
11 Nov 2024	437.7 µg/m³

Daily means, the highest since 17 Oct 2024; 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, Angra do Heroísmo, Portugal, 17 Oct 2024 – 12 Oct 2026. Monitor data from EEA, via OpenAQ and from the publisher directly; sources listed at smogrank.com/sources. smogrank.com/pt/angra-do-heroismo/history (accessed 13 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.

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

Updated 2026-10-13 23:07 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).