SmogRank / World / United States / California / October 2024

Most unhealthy days in California, United States, October 2024

117 cities in California, United States ranked by their share of unhealthy days over the 31 days. The most unhealthy days: Calexico, United States, 1 of 28 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.

← Calexico 4% 3%0
Every city in California, United States ranked for October 2024, 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. 1Calexico
    1 of 28
  2. 2Redding
    1 of 31
  3. 3Red Bluff
    1 of 31
  4. 4Jurupa Valley
    0 of 31
  5. 5Los Angeles
    0 of 31
  6. 6Visalia
    0 of 29
  7. 7Fontana
    0 of 31
  8. 8Riverside
    0 of 29
  9. 9Imperial Beach
    0 of 31
  10. 10Hawthornelow-cost sensors
    0 of 30
  11. 11Inglewoodlow-cost sensors
    0 of 30
  12. 12Burbank
    0 of 31
  13. 13Carsonlow-cost sensors
    0 of 30
  14. 13Fresno
    0 of 31
  15. 15Hanford
    0 of 29
  16. 16Anaheim
    0 of 31
  17. 17Compton
    0 of 28
  18. 18Santa Monicalow-cost sensors
    0 of 31
  19. 18Torrancelow-cost sensors
    0 of 30
  20. 20Clovis
    0 of 30
  21. 20Santa Clarita
    0 of 31
  22. 22Bakersfield
    0 of 31
  23. 22Porterville
    0 of 29
  24. 24Glendora
    0 of 31
  25. 25Corcoran
    0 of 28
  26. 26Chula Vista
    0 of 31
  27. 27Lomitalow-cost sensors
    0 of 30
  28. 28Long Beach
    0 of 31
  29. 29La Crescenta-Montroselow-cost sensors
    0 of 30
  30. 30Agouralow-cost sensors
    0 of 30
  31. 31San Diego
    0 of 31
  32. 32El Cajon
    0 of 31
  33. 33Santa Barbara
    0 of 30
  34. 34Rio Vista
    0 of 31
  35. 35Brawley
    0 of 31
  36. 35Victorville
    0 of 31
  37. 37Indio
    0 of 31
  38. 38Stockton
    0 of 29
  39. 39Berkeley
    0 of 30
  40. 40Richmond
    0 of 30
  41. 41Madera
    0 of 30
  42. 42Colusa
    0 of 25
  43. 42Woodland
    0 of 31
  44. 44Poway
    0 of 31
  45. 44San Jose
    0 of 31
  46. 46Turlock
    0 of 30
  47. 46Arden-Arcade
    0 of 25
  48. 48Lake Elsinore
    0 of 29
  49. 49Hollister
    0 of 30
  50. 50Oceanside
    0 of 31
  51. 50Willows
    0 of 27
  52. 52Sacramento
    0 of 31
  53. 53Manteca
    0 of 30
  54. 54Oakland
    0 of 31
  55. 54Simi Valley
    0 of 31
  56. 56Modesto
    0 of 24
  57. 57Guadalupe
    0 of 31
  58. 57Yuba City
    0 of 29
  59. 59El Centro
    0 of 31
  60. 60Martinez
    0 of 27
  61. 60Vallejo
    0 of 27
  62. 62Thousand Oaks
    0 of 31
  63. 63Banning
    0 of 31
  64. 63Gridley
    0 of 29
  65. 65Chico
    0 of 28
  66. 65Goletalow-cost sensors
    0 of 30
  67. 67Ben Lomond
    0 of 28
  68. 67King City
    0 of 30
  69. 69Fillmore
    0 of 31
  70. 70Alpine
    0 of 31
  71. 70Huron
    0 of 26
  72. 72Salinas
    0 of 31
  73. 72Crescent City
    0 of 29
  74. 74South Lake Tahoe
    0 of 29
  75. 75Lancaster
    0 of 31
  76. 75Prunedalelow-cost sensors
    0 of 27
  77. 75Roseville
    0 of 29
  78. 78Crestline
    0 of 31
  79. 79Carpinteria
    0 of 27
  80. 79Merced
    0 of 30
  81. 79Orcutt
    0 of 30
  82. 82El Rio
    0 of 31
  83. 82Live Oaklow-cost sensors
    0 of 28
  84. 82San Leandro
    0 of 30
  85. 82Watsonvillelow-cost sensors
    0 of 28
  86. 86Redwood City
    0 of 29
  87. 86Santa Cruz
    0 of 31
  88. 88Livermore
    0 of 30
  89. 88Ojai
    0 of 31
  90. 90Lompoc
    0 of 27
  91. 90Tracy
    0 of 28
  92. 92Oceano
    0 of 31
  93. 93Davis
    0 of 29
  94. 93Galt
    0 of 27
  95. 93San Rafael
    0 of 30
  96. 96Atascadero
    0 of 31
  97. 96San Luis Obispo
    0 of 31
  98. 96Seasidelow-cost sensors
    0 of 28
  99. 99Lincoln
    0 of 29
  100. 99North Auburn
    0 of 28
  101. 99Ridgecrest
    0 of 31
  102. 99Sunnyvalelow-cost sensors
    0 of 28
  103. 103Big Bear City
    0 of 30
  104. 104Palo Altolow-cost sensors
    0 of 28
  105. 105Pleasanton
    0 of 31
  106. 105Vacaville
    0 of 31
  107. 107Folsom
    0 of 25
  108. 108Truckee
    0 of 29
  109. 108Yreka
    0 of 31
  110. 110Gilroy
    0 of 28
  111. 111Grass Valley
    0 of 31
  112. 112Alta Sierra
    0 of 31
  113. 112Sebastopol
    0 of 26
  114. 112Solvang
    0 of 27
  115. 115Florinlow-cost sensors
    0 of 30
  116. 115Rancho Murieta
    0 of 29
  117. 117Concord
    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 2024 · All cities in United States, October 2024 · California now

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SmogRank, most polluted cities in California, United States, by unhealthy days, PM2.5, October 2024, smogrank.com/us/region/california/history/2024-10?by=days (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.