SmogRank / World / United States / California / September 2024

Most unhealthy days in California, United States, September 2024

112 cities in California, United States ranked by their share of unhealthy days over the 30 days. The most unhealthy days: Big Bear City, United States, 7 of 24 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.

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

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 2024 · All cities in United States, September 2024 · California now

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SmogRank, most polluted cities in California, United States, by unhealthy days, PM2.5, September 2024, smogrank.com/us/region/california/history/2024-09?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.