SmogRank / World / United States / California / January 2023

Most polluted cities in California, United States, January 2023

86 cities in California, United States ranked by their average PM2.5 over the 31 days. Worst: Calexico at 12.8 µg/m³, #317 of 1,225 cities in the world. Cleanest: Tracy at 3.2. A city needs measurements on 70% of the days to be ranked.

OpenAQ's archive, where our readings come from, has almost none for 7 of these 31 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.

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

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SmogRank, most polluted cities in California, United States, PM2.5, January 2023, smogrank.com/us/region/california/history/2023-01 (accessed 6 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.