SmogRank / World / United States / California / August 2025

Most polluted cities in California, United States, August 2025

123 cities in California, United States ranked by their average PM2.5 over the 31 days. Worst: Fontana at 14.2 µg/m³, #401 of 2,841 cities in the world. Cleanest: Sebastopol at 2.4. 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 6% 6%0
Every city in California, United States ranked for August 2025, 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. 2Fillmore
    3%
  3. 3Fontana
    0%
  4. 4Jurupa Valley
    0%
  5. 5Bakersfield
    0%
  6. 6Riverside
    0%
  7. 7Glendora
    0%
  8. 8Imperial Beach
    0%
  9. 9Los Angeles
    0%
  10. 10Santa Barbara
    0%
  11. 11Burbank
    0%
  12. 12Santa Monicalow-cost sensors
    0%
  13. 13Agouralow-cost sensors
    0%
  14. 14Corcoran
    0%
  15. 14Hawthornelow-cost sensors
    0%
  16. 16San Diego
    0%
  17. 16Victorville
    0%
  18. 18El Centro
    0%
  19. 19Compton
    0%
  20. 20Calexico
    0%
  21. 20Indio
    0%
  22. 20Santa Clarita
    0%
  23. 23Poway
    0%
  24. 23La Crescenta-Montroselow-cost sensors
    0%
  25. 25Long Beach
    0%
  26. 26Carsonlow-cost sensors
    0%
  27. 26Lake Elsinore
    0%
  28. 28Banning
    0%
  29. 28El Cajon
    0%
  30. 28Porterville
    0%
  31. 28Simi Valley
    0%
  32. 32Torrancelow-cost sensors
    0%
  33. 33Alpine
    0%
  34. 34Inglewoodlow-cost sensors
    0%
  35. 35Lomitalow-cost sensors
    0%
  36. 36Oceanside
    0%
  37. 37Ojai
    0%
  38. 37Rio Vista
    0%
  39. 39Santa Paula
    0%
  40. 39Thousand Oaks
    0%
  41. 41Anaheim
    0%
  42. 41Visalia
    0%
  43. 43Brawley
    0%
  44. 44Hanford
    0%
  45. 45Madera
    0%
  46. 46Fresno
    0%
  47. 47Temecula
    0%
  48. 48Crestline
    0%
  49. 49Colusa
    0%
  50. 50El Rio
    0%
  51. 50Richmond
    0%
  52. 52Berkeley
    0%
  53. 53Clovis
    0%
  54. 53South Lake Tahoe
    0%
  55. 55San Jose
    0%
  56. 56Chico
    0%
  57. 57Lancaster
    0%
  58. 58Lompoc
    0%
  59. 59Huron
    0%
  60. 60Woodland
    0%
  61. 61Goletalow-cost sensors
    0%
  62. 62San Luis Obispo
    0%
  63. 63Carpinteria
    0%
  64. 64Red Bluff
    0%
  65. 65Oceano
    0%
  66. 66Oakland
    0%
  67. 66Willows
    0%
  68. 68Lincoln
    0%
  69. 68Merced
    0%
  70. 68Vallejo
    0%
  71. 68Yuba City
    0%
  72. 72Guadalupe
    0%
  73. 72Stockton
    0%
  74. 72Turlock
    0%
  75. 72Redding
    0%
  76. 76Davis
    0%
  77. 76King City
    0%
  78. 76Prunedalelow-cost sensors
    0%
  79. 76San Leandro
    0%
  80. 80Folsom
    0%
  81. 80Gridley
    0%
  82. 80Live Oaklow-cost sensors
    0%
  83. 80Tracy
    0%
  84. 84Big Bear City
    0%
  85. 84Galt
    0%
  86. 84Roseville
    0%
  87. 87Paradise
    0%
  88. 87Watsonvillelow-cost sensors
    0%
  89. 89Grass Valley
    0%
  90. 89Salinas
    0%
  91. 89Truckee
    0%
  92. 89Vacaville
    0%
  93. 93North Auburn
    0%
  94. 94Florinlow-cost sensors
    0%
  95. 94Gilroy
    0%
  96. 94Hollister
    0%
  97. 94Manteca
    0%
  98. 94Pleasanton
    0%
  99. 94Solvang
    0%
  100. 94South San Franciscolow-cost sensors
    0%
  101. 94Arden-Arcade
    0%
  102. 102Modesto
    0%
  103. 103Palo Altolow-cost sensors
    0%
  104. 103Seasidelow-cost sensors
    0%
  105. 105San Francisco
    0%
  106. 105Windsorlow-cost sensors
    0%
  107. 107Ridgecrest
    0%
  108. 108Alta Sierra
    0%
  109. 108Ben Lomond
    0%
  110. 108Orcutt
    0%
  111. 108Crescent City
    0%
  112. 112Martinez
    0%
  113. 112Ukiah
    0%
  114. 114Redwood City
    0%
  115. 115Rancho Murieta
    0%
  116. 116Santa Cruz
    0%
  117. 117Sacramento
    0%
  118. 117San Rafael
    0%
  119. 119Concord
    0%
  120. 120Sunnyvalelow-cost sensors
    0%
  121. 121Atascadero
    0%
  122. 122Livermore
    0%
  123. 123Sebastopol
    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, August 2025 · All cities in United States, August 2025 · California now

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SmogRank, most polluted cities in California, United States, PM2.5, August 2025, smogrank.com/us/region/california/history/2025-08 (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.