SmogRank / World / United States / California / September 2026

Most polluted cities in California, United States, September 2026

125 cities in California, United States ranked by their average PM2.5 over the 30 days. Worst: Jurupa Valley at 13.0 µg/m³, #449 of 2,949 cities in the world. Cleanest: San Mateo at 1.3. 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.

← Jurupa Valley 0% 0.75%0
Every city in California, United States ranked for September 2026, 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. 1Jurupa Valley
    0%
  2. 2Riverside
    0%
  3. 3Imperial Beach
    0%
  4. 4Hanford
    0%
  5. 5Oceanside
    0%
  6. 6Mecca
    0%
  7. 7Cambria
    0%
  8. 8Corcoran
    0%
  9. 8Fontana
    0%
  10. 10Clovis
    0%
  11. 11Fresno
    0%
  12. 12Los Angeles
    0%
  13. 12Whittier
    0%
  14. 14Compton
    0%
  15. 14San Diego
    0%
  16. 16Richmond
    0%
  17. 16Tularelow-cost sensors
    0%
  18. 18Chula Vista
    0%
  19. 19Hawthornelow-cost sensors
    0%
  20. 20Glendora
    0%
  21. 21Madera
    0%
  22. 22Mission Viejo
    0%
  23. 23Bakersfield
    0%
  24. 23Carsonlow-cost sensors
    0%
  25. 23Inglewoodlow-cost sensors
    0%
  26. 23Merced
    0%
  27. 23Oceano
    0%
  28. 23Porterville
    0%
  29. 23Santa Clarita
    0%
  30. 23Santa Monicalow-cost sensors
    0%
  31. 31Agouralow-cost sensors
    0%
  32. 31Burbank
    0%
  33. 33Lake Elsinore
    0%
  34. 34Anaheim
    0%
  35. 34El Cajon
    0%
  36. 36Ben Lomond
    0%
  37. 36Poway
    0%
  38. 38Long Beach
    0%
  39. 39San Jose
    0%
  40. 39Turlock
    0%
  41. 41Orcutt
    0%
  42. 42Lomitalow-cost sensors
    0%
  43. 42Manteca
    0%
  44. 42Salinas
    0%
  45. 45Carpinteria
    0%
  46. 45San Leandro
    0%
  47. 47Torrancelow-cost sensors
    0%
  48. 48Yuba City
    0%
  49. 49Calexico
    0%
  50. 49Elk Grovelow-cost sensors
    0%
  51. 51Gridley
    0%
  52. 51Livermore
    0%
  53. 51Redwood City
    0%
  54. 51South Lake Tahoe
    0%
  55. 51Victorville
    0%
  56. 51La Crescenta-Montroselow-cost sensors
    0%
  57. 57Alta Sierra
    0%
  58. 57Guadalupe
    0%
  59. 57Prunedalelow-cost sensors
    0%
  60. 57San Francisco
    0%
  61. 57Simi Valley
    0%
  62. 62Brawley
    0%
  63. 62Morro Bay
    0%
  64. 62Thousand Oaks
    0%
  65. 62Willows
    0%
  66. 66Fillmore
    0%
  67. 66Banning
    0%
  68. 66Davis
    0%
  69. 66Delanolow-cost sensors
    0%
  70. 66Stockton
    0%
  71. 71Berkeley
    0%
  72. 71Colusa
    0%
  73. 71King City
    0%
  74. 71Vallejo
    0%
  75. 71Arden-Arcade
    0%
  76. 76Alpine
    0%
  77. 76El Rio
    0%
  78. 76Huron
    0%
  79. 76Lincoln
    0%
  80. 80Temecula
    0%
  81. 81Galt
    0%
  82. 81Goletalow-cost sensors
    0%
  83. 81Santa Cruz
    0%
  84. 84Concord
    0%
  85. 85Florinlow-cost sensors
    0%
  86. 85Oakland
    0%
  87. 85Roseville
    0%
  88. 88El Centro
    0%
  89. 88Redding
    0%
  90. 90Gilroy
    0%
  91. 90Sacramento
    0%
  92. 90Seasidelow-cost sensors
    0%
  93. 90South San Franciscolow-cost sensors
    0%
  94. 94Solvang
    0%
  95. 95Crestline
    0%
  96. 95Modesto
    0%
  97. 95Ukiah
    0%
  98. 98Paradise
    0%
  99. 99Tracy
    0%
  100. 99Truckee
    0%
  101. 99Watsonvillelow-cost sensors
    0%
  102. 99Red Bluff
    0%
  103. 103Ojai
    0%
  104. 103Rancho Murieta
    0%
  105. 103Windsorlow-cost sensors
    0%
  106. 106Chico
    0%
  107. 106Los Banoslow-cost sensors
    0%
  108. 108Atascadero
    0%
  109. 108Ridgecrest
    0%
  110. 108San Rafael
    0%
  111. 111Indio
    0%
  112. 111North Auburn
    0%
  113. 113Hollister
    0%
  114. 114Lancaster
    0%
  115. 115Folsom
    0%
  116. 115Sebastopol
    0%
  117. 117Fremontlow-cost sensors
    0%
  118. 117Palo Altolow-cost sensors
    0%
  119. 119Lompoc
    0%
  120. 120Yreka
    0%
  121. 121Sunnyvalelow-cost sensors
    0%
  122. 121Vacaville
    0%
  123. 123Cereslow-cost sensors
    0%
  124. 124Big Bear City
    0%
  125. 125San Mateolow-cost sensors
    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 2026 · All cities in United States, September 2026 · California now

Use this board

SmogRank, most polluted cities in California, United States, PM2.5, September 2026, smogrank.com/us/region/california/history/2026-09 (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.