SmogRank / United States / California / Seaside

Seaside, month by month

Seaside has a measured daily mean on 544 days since 26 April 2024. Its worst month was December 2024, at 41 US AQI (7.3 µg/m³), 1,608th of 2,616 cities on that month's world ranking. Its cleanest was February 2026, at 24 US AQI (4.3 µg/m³).

Every month since 2024

2026too few days for a mean (a year needs 199)131 days measured
Jan26#2,382Feb24#2,689Mar29#2,638Apr2 daysMay5 daysJun5 daysJul6 daysAug9 daysSep32#1,947Oct38#1,426
2025too few days for a mean (a year needs 256)206 days measured
Jan14 daysFeb14 daysMar19 daysApr15 daysMay4 daysJun5 daysJul19 daysAug29#2,649Sep34#2,057Oct21 daysNov30#2,321Dec28#2,673
2024too few days for a mean (a year needs 257)207 days measured
JanFebMarApr5 daysMay29#2,222Jun33#2,022Jul33#1,972Aug32#1,783Sep13 daysOct28#1,756Nov29#2,214Dec41#1,608
Each square is a month's mean PM2.5 in US AQI from Seaside'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 Seaside 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

15 months
MonthWhy
Aug 20269 of 31 days measured; a month needs 22. The others: 22 with under 18 hours of readings or readings that failed our checks.
Jul 20266 of 31 days measured; a month needs 22. The others: 25 with under 18 hours of readings or readings that failed our checks.
Jun 20265 of 30 days measured; a month needs 21. The others: 25 with under 18 hours of readings or readings that failed our checks.
May 20265 of 31 days measured; a month needs 22. The others: 26 with under 18 hours of readings or readings that failed our checks.
Apr 20262 of 30 days measured; a month needs 21. The others: 28 with under 18 hours of readings or readings that failed our checks.
Oct 202521 of 31 days measured; a month needs 22. The others: 10 with under 18 hours of readings or readings that failed our checks.
Jul 202519 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Jun 20255 of 30 days measured; a month needs 21. The others: 25 with under 18 hours of readings or readings that failed our checks.
May 20254 of 31 days measured; a month needs 22. The others: 27 with under 18 hours of readings or readings that failed our checks.
Apr 202515 of 30 days measured; a month needs 21. The others: 15 with under 18 hours of readings or readings that failed our checks.
Mar 202519 of 31 days measured; a month needs 22. The others: 12 with under 18 hours of readings or readings that failed our checks.
Feb 202514 of 28 days measured; a month needs 20. The others: 14 with under 18 hours of readings or readings that failed our checks.
Jan 202514 of 31 days measured; a month needs 22. The others: 17 with under 18 hours of readings or readings that failed our checks.
Sep 202413 of 30 days measured; a month needs 21. The others: 17 with under 18 hours of readings or readings that failed our checks.
Apr 20245 of 30 days measured; a month needs 21.

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

Seaside's worst months

MonthUS AQIDays measuredWorld rank
December 2024 417.3 µg/m³30 of 311,608thof 2,616
September 2025 346.1 µg/m³24 of 302,057thof 3,104
June 2024 336.0 µg/m³27 of 302,022ndof 2,563
July 2024 336.0 µg/m³26 of 311,972ndof 2,566
August 2024 325.8 µg/m³22 of 311,783rdof 2,010
September 2026 325.7 µg/m³25 of 301,947thof 2,981

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.

Seaside's worst days

DayUS AQI
8 Nov 2024 7320.9 µg/m³
8 Dec 2024 6717.8 µg/m³
11 Dec 2024 6416.0 µg/m³
18 Jan 2025 5812.9 µg/m³
19 Jan 2025 5812.6 µg/m³
7 Dec 2024 5712.5 µg/m³
22 Dec 2024 5712.1 µg/m³
30 Nov 2025 5712.1 µg/m³
6 Jun 2024 5611.8 µg/m³
5 Dec 2024 5511.3 µg/m³

Daily means, the highest since 26 Apr 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, Seaside, United States, 26 Apr 2024 – 11 Oct 2026. Monitor data from Clarity via OpenAQ; sources listed at smogrank.com/sources. smogrank.com/us/seaside/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.

Seaside 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).