SmogRank / World / United States / California / September 2023

Most polluted cities in California, United States, September 2023

105 cities in California, United States ranked by their average PM2.5 over the 30 days. Worst: Yreka at 20.7 µg/m³, #89 of 2,128 cities in the world. Cleanest: Big Bear City at 4.3. A city needs measurements on 70% of the days to be ranked.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

← Yreka 17% 10%0
Every city in California, United States ranked for September 2023, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.
  1. 1Yreka
    17%
  2. 2Crescent City
    12%
  3. 3Richmond
    11%
  4. 4Rio Vista
    7%
  5. 5Sebastopol
    7%
  6. 6Redwood City
    4%
  7. 7Stockton
    4%
  8. 8Salinas
    4%
  9. 9Hollister
    4%
  10. 10King City
    4%
  11. 11Ben Lomond
    4%
  12. 12Oakland
    3%
  13. 13San Jose
    3%
  14. 14Manteca
    3%
  15. 15Livermore
    3%
  16. 16San Leandro
    3%
  17. 17San Rafael
    3%
  18. 18Galt
    3%
  19. 19Concord
    3%
  20. 20Gilroy
    3%
  21. 21Fontana
    0%
  22. 21Indio
    0%
  23. 23Riverside
    0%
  24. 24Compton
    0%
  25. 25Jurupa Valley
    0%
  26. 26Anaheim
    0%
  27. 27Los Angeles
    0%
  28. 28Long Beach
    0%
  29. 28La Crescenta-Montroselow-cost sensors
    0%
  30. 30Bakersfield
    0%
  31. 30Glendora
    0%
  32. 32Madera
    0%
  33. 33Fresno
    0%
  34. 33Porterville
    0%
  35. 35Turlock
    0%
  36. 36Chula Vista
    0%
  37. 36Hanford
    0%
  38. 36Oceano
    0%
  39. 39Oceanside
    0%
  40. 39Santa Clarita
    0%
  41. 39Visalia
    0%
  42. 42Agouralow-cost sensors
    0%
  43. 43Carsonlow-cost sensors
    0%
  44. 43Torrancelow-cost sensors
    0%
  45. 45San Diego
    0%
  46. 46Lompoc
    0%
  47. 46Santa Barbara
    0%
  48. 48Burbank
    0%
  49. 48Hawthornelow-cost sensors
    0%
  50. 50Inglewoodlow-cost sensors
    0%
  51. 50Santa Monicalow-cost sensors
    0%
  52. 52Brawley
    0%
  53. 52Modesto
    0%
  54. 54Guadalupe
    0%
  55. 55El Cajon
    0%
  56. 55Lomitalow-cost sensors
    0%
  57. 57Banning
    0%
  58. 57Clovis
    0%
  59. 57Corcoran
    0%
  60. 57Poway
    0%
  61. 61Thousand Oaks
    0%
  62. 62Carpinteria
    0%
  63. 63Colusa
    0%
  64. 64Davis
    0%
  65. 65Simi Valley
    0%
  66. 66El Centro
    0%
  67. 66Yuba City
    0%
  68. 68Folsom
    0%
  69. 68Ukiah
    0%
  70. 70Solvang
    0%
  71. 71Victorville
    0%
  72. 72Lincoln
    0%
  73. 72San Luis Obispo
    0%
  74. 74Merced
    0%
  75. 75Calexico
    0%
  76. 75Huron
    0%
  77. 77Alpine
    0%
  78. 77Woodland
    0%
  79. 79Roseville
    0%
  80. 80Ojai
    0%
  81. 81Lake Elsinore
    0%
  82. 82Paradise
    0%
  83. 83Sacramento
    0%
  84. 83Willows
    0%
  85. 85Fillmore
    0%
  86. 85Gridley
    0%
  87. 85North Auburn
    0%
  88. 85Rancho Murieta
    0%
  89. 85Santa Cruz
    0%
  90. 90Chico
    0%
  91. 91Orcutt
    0%
  92. 92Crestline
    0%
  93. 93Atascadero
    0%
  94. 94Alta Sierra
    0%
  95. 94Anderson
    0%
  96. 94Red Bluff
    0%
  97. 94Redding
    0%
  98. 98Tracy
    0%
  99. 99Grass Valley
    0%
  100. 100Truckee
    0%
  101. 100Vacaville
    0%
  102. 102Arden-Arcade
    0%
  103. 103South Lake Tahoe
    0%
  104. 104Lancaster
    0%
  105. 105Big Bear City
    0%

Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.

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

All cities in the world, September 2023 · All cities in United States, September 2023 · California now

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SmogRank, most polluted cities in California, United States, PM2.5, September 2023, smogrank.com/us/region/california/history/2023-09 (accessed 7 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.