SmogRank / Episodes / United States

California, United States, July 2023

For 2 days, from 4 to 5 July 2023, 12 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Glendora, California, United States: 111.0 µg/m³ on 5 July, about 8.7× its usual 12.8.

Likely Independence Day fireworksIt came on 4 and 5 July, when fireworks smoke fills the air over many US cities at once.
Cities reached12in 1 country
Days24 to 5 July 2023
Worst day5 July11 cities counted
Furthest above usual8.7×Glendora

Day by day

5 July 11 cities at twice their usual or more
Lake ElsinoreBanningOceansidePowayEl CajonIndioSan DiegoChula VistaVictorvilleTijuanaCarsonLomitaTorranceHawthorneInglewoodSanta MonicaLancasterBrawleyAgouraCalexicoSimi ValleyMexicaliThousand OaksFillmoreYumaBakersfieldSanta BarbaraEnterpriseHendersonBoulder CityLompocOrcuttNipomoArroyo GrandeSan Luis ObispoAtascaderoGlendaleSanta ClaritaLos AngelesLong BeachEl CentroBurbankLa Crescenta-MontroseComptonAnaheimJurupa ValleyRiversideFontanaGlendora
1 Jul2345678
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

AnaheimAnaheim, 1 July: 9.6 µg/m³, 1.0× usualAnaheim, 2 July: 10.7 µg/m³, 1.1× usualAnaheim, 3 July: 14.0 µg/m³, 1.4× usualAnaheim, 4 July: 46.3 µg/m³, 4.6× usualAnaheim, 5 July: 31.8 µg/m³, 3.1× usualAnaheim, 6 July: 10.8 µg/m³, 1.1× usualAnaheim, 7 July: 8.9 µg/m³, 0.9× usualAnaheim, 8 July: 9.9 µg/m³, 1.0× usualGlendoraGlendora, 1 July: 15.8 µg/m³, 1.2× usualGlendora, 2 July: 18.1 µg/m³, 1.4× usualGlendora, 3 July: 18.0 µg/m³, 1.4× usualGlendora, 4 July: 38.5 µg/m³, 3.0× usualGlendora, 5 July: 111.0 µg/m³, 8.7× usualGlendora, 6 July: 13.1 µg/m³, 1.0× usualGlendora, 7 July: 11.9 µg/m³, 0.9× usualGlendora, 8 July: 13.2 µg/m³, 1.0× usualComptonCompton, 1 July: 13.6 µg/m³, 1.3× usualCompton, 2 July: 19.2 µg/m³, 1.8× usualCompton, 3 July: 15.0 µg/m³, 1.4× usualCompton, 4 July: 31.6 µg/m³, 3.0× usualCompton, 5 July: 30.9 µg/m³, 2.9× usualCompton, 6 July: 11.8 µg/m³, 1.1× usualCompton, 7 July: 9.3 µg/m³, 0.9× usualCompton, 8 July: 10.6 µg/m³, 1.0× usualLos AngelesLos Angeles, 1 July: 22.1 µg/m³, 1.7× usualLos Angeles, 2 July: 17.0 µg/m³, 1.3× usualLos Angeles, 3 July: 18.9 µg/m³, 1.4× usualLos Angeles, 4 July: 31.3 µg/m³, 2.4× usualLos Angeles, 5 July: 31.9 µg/m³, 2.4× usualLos Angeles, 6 July: 18.0 µg/m³, 1.4× usualLos Angeles, 7 July: 14.3 µg/m³, 1.1× usualLos Angeles, 8 July: 15.3 µg/m³, 1.2× usualLong BeachLong Beach, 1 July: 11.1 µg/m³, 1.2× usualLong Beach, 2 July: 14.7 µg/m³, 1.5× usualLong Beach, 3 July: 15.6 µg/m³, 1.6× usualLong Beach, 4 July: 25.0 µg/m³, 2.6× usualLong Beach, 5 July: 23.4 µg/m³, 2.5× usualLong Beach, 6 July: 10.8 µg/m³, 1.1× usualLong Beach, 7 July: 8.8 µg/m³, 0.9× usualLong Beach, 8 July: 9.2 µg/m³, 1.0× usualFontanaFontana, 1 July: 17.8 µg/m³, 1.2× usualFontana, 2 July: 19.6 µg/m³, 1.4× usualFontana, 3 July: 19.1 µg/m³, 1.3× usualFontana, 4 July: 26.2 µg/m³, 1.8× usualFontana, 5 July: 106.0 µg/m³, 7.3× usualFontana, 6 July: 13.5 µg/m³, 0.9× usualFontana, 7 July: 13.2 µg/m³, 0.9× usualFontana, 8 July: 14.4 µg/m³, 1.0× usualRiversideRiverside, 1 July: 14.4 µg/m³, 1.1× usualRiverside, 2 July: 16.7 µg/m³, 1.3× usualRiverside, 3 July: 15.1 µg/m³, 1.2× usualRiverside, 4 July: 22.4 µg/m³, 1.7× usualRiverside, 5 July: 74.1 µg/m³, 5.7× usualRiverside, 6 July: 14.0 µg/m³, 1.1× usualRiverside, 7 July: 13.4 µg/m³, 1.0× usualRiverside, 8 July: 12.7 µg/m³, 1.0× usualJurupa ValleyJurupa Valley, 1 July: 14.2 µg/m³, 1.0× usualJurupa Valley, 2 July: 17.4 µg/m³, 1.3× usualJurupa Valley, 3 July: 15.7 µg/m³, 1.1× usualJurupa Valley, 4 July: 18.8 µg/m³, 1.4× usualJurupa Valley, 5 July: 74.0 µg/m³, 5.4× usualJurupa Valley, 6 July: 13.9 µg/m³, 1.0× usualJurupa Valley, 7 July: 12.4 µg/m³, 0.9× usualJurupa Valley, 8 July: 14.3 µg/m³, 1.0× usualBurbankBurbank, 1 July: 16.6 µg/m³, 1.4× usualBurbank, 2 July: 13.5 µg/m³, 1.2× usualBurbank, 3 July: 13.1 µg/m³, 1.1× usualBurbank, 4 July: 20.8 µg/m³, 1.8× usualBurbank, 5 July: 32.3 µg/m³, 2.8× usualBurbank, 6 July: 13.2 µg/m³, 1.1× usualBurbank, 7 July: 14.0 µg/m³, 1.2× usualBurbank, 8 July: 12.4 µg/m³, 1.1× usualLa Crescenta-Montro…La Crescenta-Montrose, 1 July: 15.8 µg/m³, 1.6× usualLa Crescenta-Montrose, 2 July: 13.9 µg/m³, 1.4× usualLa Crescenta-Montrose, 3 July: 12.1 µg/m³, 1.2× usualLa Crescenta-Montrose, 4 July: 12.7 µg/m³, 1.3× usualLa Crescenta-Montrose, 5 July: 28.6 µg/m³, 2.9× usualLa Crescenta-Montrose, 6 July: 13.0 µg/m³, 1.3× usualLa Crescenta-Montrose, 7 July: 15.8 µg/m³, 1.6× usualLa Crescenta-Montrose, 8 July: 14.0 µg/m³, 1.4× usualEl CentroEl Centro, 1 July: 16.3 µg/m³, 1.7× usualEl Centro, 2 July: 14.3 µg/m³, 1.5× usualEl Centro, 3 July: 13.1 µg/m³, 1.4× usualEl Centro, 4 July: 11.3 µg/m³, 1.2× usualEl Centro, 5 July: 26.2 µg/m³, 2.7× usualEl Centro, 6 July: 10.0 µg/m³, 1.0× usualEl Centro, 7 July: 9.0 µg/m³, 0.9× usualEl Centro, 8 July: 13.5 µg/m³, 1.4× usualSanta ClaritaSanta Clarita, 1 July: 15.9 µg/m³, 1.4× usualSanta Clarita, 2 July: 15.0 µg/m³, 1.3× usualSanta Clarita, 3 July: 14.3 µg/m³, 1.3× usualSanta Clarita, 4 July: 17.2 µg/m³, 1.5× usualSanta Clarita, 5 July: 25.5 µg/m³, 2.2× usualSanta Clarita, 6 July: 13.7 µg/m³, 1.2× usualSanta Clarita, 7 July: 15.4 µg/m³, 1.4× usualSanta Clarita, 8 July: 14.9 µg/m³, 1.3× usual1 Jul2345678
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
GlendoraCalifornia, United States2 111.05 July12.88.7×
FontanaCalifornia, United States1 106.05 July14.57.3×
RiversideCalifornia, United States1 74.15 July12.95.7×
Jurupa ValleyCalifornia, United States1 74.05 July13.85.4×
AnaheimCalifornia, United States2 46.34 July10.14.6×
ComptonCalifornia, United States2 31.64 July10.63.0×
La Crescenta-MontroseCalifornia, United States1 28.65 July9.72.9×
BurbankCalifornia, United States1 32.35 July11.72.8×
El CentroCalifornia, United States1 26.25 July9.62.7×
Long BeachCalifornia, United States1 25.04 July9.52.6×
Los AngelesCalifornia, United States2 31.95 July13.32.4×
Santa ClaritaCalifornia, United States1 25.55 July11.42.2×

Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.

Against other episodes in the United States

Number 29 of 41 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 41.

Use this page

SmogRank, California, United States, July 2023: 12 cities with PM2.5 at twice their usual or more, 4 to 5 July 2023, smogrank.com/episodes/2023-07-california-united-states (accessed 2 October 2026).

Download top 10 (PNG)

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.