SmogRank / World / United States / California / October 2025

Most unhealthy days in California, United States, October 2025

118 cities in California, United States ranked by their share of unhealthy days over the 31 days. The most unhealthy days: Tulare, United States, 9 of 31 measured days. 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.

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

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, October 2025 · All cities in United States, October 2025 · California now

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SmogRank, most polluted cities in California, United States, by unhealthy days, PM2.5, October 2025, smogrank.com/us/region/california/history/2025-10?by=days (accessed 7 Oct 2026).

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