SmogRank / World / United States / California / 2023

Most polluted cities in California, United States, 2023

93 cities in California, United States ranked by their average PM2.5 over the 365 days; 85 above the WHO annual guideline (5.0 µg/m³). Worst: Compton at 12.7 µg/m³, #167 of 1,302 cities in the world. Cleanest: Lancaster at 4.2. A city needs measurements on 70% of the days to be ranked.

OpenAQ's archive, where our readings come from, has almost none for 56 of these 365 days. Cities in the United States and Europe have them from the EPA's and the European Environment Agency's own records of the same monitors; elsewhere a city's average is over its other days. Why.

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 6% 5%0
Every city in California, United States ranked for 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
    6%
  2. 2Hanford
    3%
  3. 3Stockton
    2%
  4. 4Fresno
    2%
  5. 5Bakersfield
    2%
  6. 6Visalia
    1%
  7. 7Red Bluff
    1%
  8. 8Rio Vista
    1%
  9. 9Manteca
    1%
  10. 10Modesto
    1%
  11. 11Redding
    1%
  12. 12Richmond
    1%
  13. 13Turlock
    1%
  14. 14Brawley
    1%
  15. 15Sebastopol
    1%
  16. 16Glendora
    1%
  17. 17Riverside
    1%
  18. 18Ukiah
    1%
  19. 19Banning
    1%
  20. 20Corcoran
    1%
  21. 21Jurupa Valley
    1%
  22. 22Ben Lomond
    0%
  23. 23Hawthornelow-cost sensors
    0%
  24. 24Carsonlow-cost sensors
    0%
  25. 25Compton
    0%
  26. 26Galt
    0%
  27. 27North Auburn
    0%
  28. 28Concord
    0%
  29. 29Oceano
    0%
  30. 30San Francisco
    0%
  31. 31Redwood City
    0%
  32. 32Calexico
    0%
  33. 33Livermore
    0%
  34. 34Hollister
    0%
  35. 35Gilroy
    0%
  36. 36Anaheim
    0%
  37. 37Salinas
    0%
  38. 38San Rafael
    0%
  39. 39San Jose
    0%
  40. 40San Leandro
    0%
  41. 41Oakland
    0%
  42. 42Madera
    0%
  43. 43Merced
    0%
  44. 44Los Angeles
    0%
  45. 45Burbank
    0%
  46. 46Porterville
    0%
  47. 47Long Beach
    0%
  48. 47Torrancelow-cost sensors
    0%
  49. 49San Diego
    0%
  50. 50Santa Clarita
    0%
  51. 51Inglewoodlow-cost sensors
    0%
  52. 52Clovis
    0%
  53. 52El Cajon
    0%
  54. 52La Crescenta-Montroselow-cost sensors
    0%
  55. 55Santa Monicalow-cost sensors
    0%
  56. 56Lomitalow-cost sensors
    0%
  57. 57Yuba City
    0%
  58. 58Oceanside
    0%
  59. 58Paradise
    0%
  60. 58Sacramento
    0%
  61. 61Arden-Arcade
    0%
  62. 62Agouralow-cost sensors
    0%
  63. 63Chico
    0%
  64. 63Victorville
    0%
  65. 65Colusa
    0%
  66. 65Santa Barbara
    0%
  67. 67Woodland
    0%
  68. 68Roseville
    0%
  69. 69Crestline
    0%
  70. 70Alta Sierra
    0%
  71. 70Huron
    0%
  72. 70Willows
    0%
  73. 73Big Bear City
    0%
  74. 73Thousand Oaks
    0%
  75. 75Lake Elsinore
    0%
  76. 76Folsom
    0%
  77. 77Lincoln
    0%
  78. 77Simi Valley
    0%
  79. 77Truckee
    0%
  80. 80Davis
    0%
  81. 80Rancho Murieta
    0%
  82. 82Grass Valley
    0%
  83. 83Fillmore
    0%
  84. 84Guadalupe
    0%
  85. 85Santa Cruz
    0%
  86. 86Ojai
    0%
  87. 87Tracy
    0%
  88. 88Lompoc
    0%
  89. 88Vacaville
    0%
  90. 90San Luis Obispo
    0%
  91. 91Orcutt
    0%
  92. 92Atascadero
    0%
  93. 93Lancaster
    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, 2023 · All cities in United States, 2023 · California now

Use this board

SmogRank, most polluted cities in California, United States, PM2.5, 2023, smogrank.com/us/region/california/history/2023 (accessed 6 Oct 2026).

Download top 10 (PNG)

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.