SmogRank / Episodes / United States

California, United States, May 2026

For 2 days, from 17 to 18 May 2026, 11 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Torrance, California, United States: 40.2 µg/m³ on 18 May, about 4.9× its usual 8.2.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached11in 1 country
Days217 to 18 May 2026
Worst day17 May7 cities counted
Furthest above usual5.3×Huntington Beach

Day by day

17 May 7 cities at twice their usual or more
Mission ViejoEncinitasLake ElsinoreAnaheimTemeculaJurupa ValleyRiversideDiamond BarWhittierLomitaCarsonFontanaGlendoraHawthorneInglewoodLos AngelesPasadenaBurbankBanningLa Crescenta-MontroseTijuanaVictorvilleAgouraSanta ClaritaThousand OaksSimi ValleyLancasterIndioFillmoreOxnardEl CentroSanta BarbaraCalexicoRidgecrestMexicaliGoletaBakersfieldLompocOrcuttYumaNipomoArroyo GrandeSan Luis ObispoAtascaderoComptonSanta MonicaImperial BeachEl CajonPowayChula VistaSan DiegoLong BeachOceansideTorranceHuntington Beach
14 May15161718192021
Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.

How it spread

Imperial BeachImperial Beach, 14 May: 7.0 µg/m³Imperial Beach, 15 May: 9.1 µg/m³Imperial Beach, 16 May: 13.1 µg/m³Imperial Beach, 17 May: 28.9 µg/m³, 3.0× its usual 9.6Imperial Beach, 18 May: 19.2 µg/m³Imperial Beach, 19 May: 18.4 µg/m³Imperial Beach, 20 May: 26.6 µg/m³Imperial Beach, 21 May: 21.8 µg/m³Huntington BeachHuntington Beach, 14 May: 1.9 µg/m³Huntington Beach, 15 May: 3.7 µg/m³Huntington Beach, 16 May: 7.4 µg/m³Huntington Beach, 17 May: 28.0 µg/m³, 5.6× its usual 4.5Huntington Beach, 18 May: 29.9 µg/m³, 5.3× its usual 5.6Huntington Beach, 19 May: 26.7 µg/m³Huntington Beach, 20 May: 22.3 µg/m³Huntington Beach, 21 May: 14.7 µg/m³PowayPoway, 14 May: 6.2 µg/m³Poway, 15 May: 9.1 µg/m³Poway, 16 May: 8.2 µg/m³Poway, 17 May: 27.9 µg/m³, 3.3× its usual 8.4Poway, 18 May: 17.5 µg/m³Poway, 19 May: 16.1 µg/m³Poway, 20 May: 18.5 µg/m³Poway, 21 May: 17.8 µg/m³San DiegoSan Diego, 14 May: 6.1 µg/m³San Diego, 15 May: 7.1 µg/m³San Diego, 16 May: 10.4 µg/m³San Diego, 17 May: 27.8 µg/m³, 3.4× its usual 8.2San Diego, 18 May: 16.8 µg/m³San Diego, 19 May: 20.0 µg/m³San Diego, 20 May: 24.4 µg/m³San Diego, 21 May: 18.4 µg/m³OceansideOceanside, 14 May: 5.6 µg/m³Oceanside, 15 May: 6.3 µg/m³Oceanside, 16 May: 8.5 µg/m³Oceanside, 17 May: 27.6 µg/m³, 3.9× its usual 7.1Oceanside, 18 May: 15.4 µg/m³Oceanside, 19 May: 18.2 µg/m³Oceanside, 20 May: 20.7 µg/m³Oceanside, 21 May: 16.2 µg/m³El CajonEl Cajon, 14 May: 6.0 µg/m³El Cajon, 15 May: 8.8 µg/m³El Cajon, 16 May: 9.2 µg/m³El Cajon, 17 May: 27.1 µg/m³, 3.2× its usual 8.6El Cajon, 18 May: 15.3 µg/m³El Cajon, 19 May: 13.7 µg/m³El Cajon, 20 May: 17.9 µg/m³El Cajon, 21 May: 16.0 µg/m³Chula VistaChula Vista, 14 May: 5.7 µg/m³Chula Vista, 15 May: 7.6 µg/m³Chula Vista, 16 May: 10.4 µg/m³Chula Vista, 17 May: 26.0 µg/m³, 3.4× its usual 7.7Chula Vista, 18 May: 16.4 µg/m³Chula Vista, 19 May: 16.0 µg/m³Chula Vista, 20 May: 22.5 µg/m³Chula Vista, 21 May: 17.1 µg/m³TorranceTorrance, 14 May: 2.1 µg/m³Torrance, 15 May: 4.5 µg/m³Torrance, 16 May: 8.0 µg/m³Torrance, 17 May: 21.0 µg/m³Torrance, 18 May: 40.2 µg/m³, 4.9× its usual 8.2Torrance, 19 May: 34.3 µg/m³Torrance, 20 May: 17.6 µg/m³Torrance, 21 May: 11.3 µg/m³Santa MonicaSanta Monica, 14 May: 6.4 µg/m³Santa Monica, 15 May: 7.4 µg/m³Santa Monica, 16 May: 8.6 µg/m³Santa Monica, 17 May: 18.3 µg/m³Santa Monica, 18 May: 28.3 µg/m³, 2.7× its usual 10.6Santa Monica, 19 May: 29.8 µg/m³Santa Monica, 20 May: 20.1 µg/m³Santa Monica, 21 May: 11.6 µg/m³Long BeachLong Beach, 14 May: 5.8 µg/m³Long Beach, 15 May: 6.9 µg/m³Long Beach, 16 May: 10.3 µg/m³Long Beach, 17 May: 21.5 µg/m³Long Beach, 18 May: 25.5 µg/m³, 3.6× its usual 7.0Long Beach, 19 May: 20.2 µg/m³Long Beach, 20 May: 16.7 µg/m³Long Beach, 21 May: 16.0 µg/m³ComptonCompton, 14 May: 7.7 µg/m³Compton, 15 May: 9.3 µg/m³Compton, 16 May: 12.8 µg/m³Compton, 17 May: 21.9 µg/m³Compton, 18 May: 25.0 µg/m³, 2.7× its usual 9.2Compton, 19 May: 22.0 µg/m³Compton, 20 May: 20.2 µg/m³Compton, 21 May: 16.5 µg/m³14 May15161718192021
Every counted city, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
Huntington BeachCalifornia, United States2 29.918 May5.65.3×
TorranceCalifornia, United States1 40.218 May8.24.9×
OceansideCalifornia, United States1 27.617 May7.13.9×
Long BeachCalifornia, United States1 25.518 May7.03.6×
San DiegoCalifornia, United States1 27.817 May8.23.4×
Chula VistaCalifornia, United States1 26.017 May7.73.4×
PowayCalifornia, United States1 27.917 May8.43.3×
El CajonCalifornia, United States1 27.117 May8.63.2×
Imperial BeachCalifornia, United States1 28.917 May9.63.0×
Santa MonicaCalifornia, United States1 28.318 May10.62.7×
ComptonCalifornia, United States1 25.018 May9.22.7×

Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.

Against other episodes in the United States

Number 88 of 130 episodes in the United States since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 130.

Use this page

SmogRank, California, United States, May 2026: 11 cities with PM2.5 at twice their usual or more, 17 to 18 May 2026, smogrank.com/episodes/2026-05-california-united-states (accessed 4 October 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes. Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.