SmogRank / World / United States / California / April 2026

Most polluted cities in California, United States, April 2026

115 cities in California, United States ranked by their average PM2.5 over the 30 days. Worst: Rio Vista at 18.5 µg/m³, #433 of 2,914 cities in the world. Cleanest: Sunnyvale at 1.0. 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.

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

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SmogRank, most polluted cities in California, United States, PM2.5, April 2026, smogrank.com/us/region/california/history/2026-04 (accessed 6 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.