SmogRank / Episodes / United States
South-western United States and Mexico, December 2024 to January 2025
For 5 days, from 29 December 2024 to 2 January 2025, 37 cities in the United States and Mexico had PM2.5 at least twice their usual for the time of year. The worst reading was Phoenix, Arizona, United States: 167.0 µg/m³ on 1 January, about 10× its usual 16.6.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 37 in 2 countries
Days 5 29 December 2024 to 2 January 2025
Worst day 1 January 34 cities counted
Furthest above usual 17× Mesa
Day by day
Play 1 January 34 cities at twice their usual or more
Victorville Banning Indio Lake Elsinore Temecula Glendora Ridgecrest Lancaster La Crescenta-Montrose Poway Enterprise Summerlin South Spring Valley Santa Clarita Santa Monica Brawley Henderson Boulder City El Centro Agoura Simi Valley Thousand Oaks Fillmore Bakersfield Oxnard Porterville Yuma Santa Barbara Goleta Corcoran Mesquite Hanford Orcutt Lompoc Nipomo Arroyo Grande San Luis Obispo Hurricane Atascadero Cedar City Merced Turlock Apache Junction Hollister Salinas Gilroy Prunedale Manteca Seaside Watsonville Tracy Live Oak Santa Cruz Galt San Jose Livermore Pleasanton Sunnyvale Casas Adobes Florin Arden-Arcade Palo Alto Sacramento Green Valley Redwood City San Leandro Concord Davis Martinez Oakland Berkeley Vacaville South San Francisco San Francisco Richmond San Rafael Santa Rosa Windsor Modesto Las Vegas Hawthorne Stockton Visalia Madera Clovis Tijuana Inglewood Torrance Nogales Fresno Carson Los Angeles Compton El Cajon Calexico Imperial Beach San Diego Fontana Long Beach Vallejo Oceanside Casa Grande Tucson Lomita Marana Anaheim Burbank Riverside Chula Vista Jurupa Valley Nogales Glendale Tempe Phoenix Mesa 26 Dec 27 28 29 30 31 1 Jan 2 3 4 5 Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.
How it spread
Jurupa Valley Jurupa Valley, 26 December: 19.4 µg/m³ Jurupa Valley, 27 December: 22.0 µg/m³ Jurupa Valley, 28 December: 35.6 µg/m³ Jurupa Valley, 29 December: 45.5 µg/m³, 3.4× its usual 13.4 Jurupa Valley, 30 December: 38.7 µg/m³, 2.9× its usual 13.5 Jurupa Valley, 31 December: 42.6 µg/m³, 3.1× its usual 13.6 Jurupa Valley, 1 January: 75.4 µg/m³, 6.1× its usual 12.4 Jurupa Valley, 2 January: 33.1 µg/m³, 2.7× its usual 12.4 Jurupa Valley, 3 January: 24.7 µg/m³ Jurupa Valley, 4 January: 44.1 µg/m³ Jurupa Valley, 5 January: 24.4 µg/m³ Anaheim Anaheim, 26 December: 13.7 µg/m³ Anaheim, 27 December: 11.4 µg/m³ Anaheim, 28 December: 24.5 µg/m³ Anaheim, 29 December: 40.0 µg/m³, 3.5× its usual 11.5 Anaheim, 30 December: 23.2 µg/m³ Anaheim, 31 December: 42.4 µg/m³, 3.6× its usual 11.7 Anaheim, 1 January: 51.0 µg/m³, 4.7× its usual 10.8 Anaheim, 2 January: 33.0 µg/m³, 3.1× its usual 10.7 Anaheim, 3 January: 22.4 µg/m³ Anaheim, 4 January: 21.7 µg/m³ Anaheim, 5 January: 21.5 µg/m³ Riverside Riverside, 26 December: 14.3 µg/m³ Riverside, 27 December: 19.4 µg/m³ Riverside, 28 December: 28.6 µg/m³ Riverside, 29 December: 36.9 µg/m³, 3.7× its usual 10.0 Riverside, 30 December: 34.9 µg/m³, 3.4× its usual 10.3 Riverside, 31 December: 34.9 µg/m³, 3.4× its usual 10.4 Riverside, 1 January: 48.5 µg/m³, 4.9× its usual 9.8 Riverside, 2 January: 17.6 µg/m³ Riverside, 3 January: 18.5 µg/m³ Riverside, 4 January: 40.5 µg/m³ Riverside, 5 January: 12.7 µg/m³ Fontana Fontana, 26 December: 12.2 µg/m³ Fontana, 27 December: 15.6 µg/m³ Fontana, 28 December: 27.3 µg/m³ Fontana, 29 December: 27.3 µg/m³, 2.8× its usual 9.6 Fontana, 30 December: 32.6 µg/m³, 3.3× its usual 9.8 Fontana, 31 December: 36.5 µg/m³, 3.7× its usual 9.8 Fontana, 1 January: 30.5 µg/m³, 3.1× its usual 10.0 Fontana, 2 January: 14.0 µg/m³ Fontana, 3 January: 19.7 µg/m³ Fontana, 4 January: 38.7 µg/m³ Fontana, 5 January: 12.4 µg/m³ Burbank Burbank, 26 December: 14.9 µg/m³ Burbank, 27 December: 14.7 µg/m³ Burbank, 28 December: 20.7 µg/m³ Burbank, 29 December: 24.2 µg/m³ Burbank, 30 December: 31.5 µg/m³, 2.9× its usual 11.0 Burbank, 31 December: 30.9 µg/m³, 2.8× its usual 11.0 Burbank, 1 January: 50.1 µg/m³, 4.8× its usual 10.5 Burbank, 2 January: 21.1 µg/m³ Burbank, 3 January: 21.4 µg/m³ Burbank, 4 January: 31.3 µg/m³ Burbank, 5 January: 11.6 µg/m³ Los Angeles Los Angeles, 26 December: 14.7 µg/m³ Los Angeles, 27 December: 12.4 µg/m³ Los Angeles, 28 December: 19.5 µg/m³ Los Angeles, 29 December: 21.4 µg/m³ Los Angeles, 30 December: 26.3 µg/m³, 2.2× its usual 12.1 Los Angeles, 31 December: 31.5 µg/m³, 2.6× its usual 12.1 Los Angeles, 1 January: 32.7 µg/m³, 3.1× its usual 10.7 Los Angeles, 2 January: 20.5 µg/m³ Los Angeles, 3 January: 25.6 µg/m³ Los Angeles, 4 January: 29.9 µg/m³ Los Angeles, 5 January: 12.7 µg/m³ Compton Compton, 26 December: 20.5 µg/m³ Compton, 27 December: 8.4 µg/m³ Compton, 28 December: 21.7 µg/m³ Compton, 29 December: 27.3 µg/m³ Compton, 30 December: 23.5 µg/m³ Compton, 31 December: 46.0 µg/m³, 2.7× its usual 16.8 Compton, 1 January: 50.9 µg/m³, 3.2× its usual 16.0 Compton, 2 January: 32.2 µg/m³, 2.0× its usual 15.9 Compton, 3 January: 22.0 µg/m³ Compton, 4 January: 25.3 µg/m³ Compton, 5 January: 23.7 µg/m³ Phoenix Phoenix, 26 December: 16.9 µg/m³ Phoenix, 27 December: 19.2 µg/m³ Phoenix, 28 December: 21.2 µg/m³ Phoenix, 29 December: 23.1 µg/m³ Phoenix, 30 December: 22.5 µg/m³ Phoenix, 31 December: 45.3 µg/m³, 2.7× its usual 16.8 Phoenix, 1 January: 167.0 µg/m³, 10× its usual 16.6 Phoenix, 2 January: 25.1 µg/m³ Phoenix, 3 January: 22.1 µg/m³ Phoenix, 4 January: 19.4 µg/m³ Phoenix, 5 January: 19.0 µg/m³ Calexico Calexico, 26 December: 14.9 µg/m³ Calexico, 27 December: no reading Calexico, 28 December: no reading Calexico, 29 December: no reading Calexico, 30 December: no reading Calexico, 31 December: 44.1 µg/m³, 3.4× its usual 13.1 Calexico, 1 January: 37.0 µg/m³, 3.3× its usual 11.3 Calexico, 2 January: 12.7 µg/m³ Calexico, 3 January: 18.4 µg/m³ Calexico, 4 January: 22.0 µg/m³ Calexico, 5 January: 8.5 µg/m³ Long Beach Long Beach, 26 December: 14.2 µg/m³ Long Beach, 27 December: 7.7 µg/m³ Long Beach, 28 December: 16.5 µg/m³ Long Beach, 29 December: 25.0 µg/m³ Long Beach, 30 December: 19.9 µg/m³ Long Beach, 31 December: 41.5 µg/m³, 3.2× its usual 12.9 Long Beach, 1 January: 43.9 µg/m³, 3.7× its usual 12.0 Long Beach, 2 January: 29.8 µg/m³, 2.6× its usual 11.4 Long Beach, 3 January: 21.8 µg/m³ Long Beach, 4 January: 17.2 µg/m³ Long Beach, 5 January: 23.2 µg/m³ Glendale Glendale, 26 December: 13.1 µg/m³ Glendale, 27 December: 12.7 µg/m³ Glendale, 28 December: 15.5 µg/m³ Glendale, 29 December: 16.3 µg/m³ Glendale, 30 December: 14.0 µg/m³ Glendale, 31 December: 40.7 µg/m³, 4.2× its usual 9.6 Glendale, 1 January: 72.9 µg/m³, 7.6× its usual 9.6 Glendale, 2 January: 14.5 µg/m³ Glendale, 3 January: 14.5 µg/m³ Glendale, 4 January: 14.1 µg/m³ Glendale, 5 January: 14.8 µg/m³ Nogales Nogales, 26 December: 15.3 µg/m³ Nogales, 27 December: 20.7 µg/m³ Nogales, 28 December: 22.7 µg/m³ Nogales, 29 December: 21.7 µg/m³ Nogales, 30 December: 23.8 µg/m³ Nogales, 31 December: 40.3 µg/m³, 2.2× its usual 18.0 Nogales, 1 January: 118.0 µg/m³, 7.0× its usual 16.9 Nogales, 2 January: 25.2 µg/m³ Nogales, 3 January: 23.1 µg/m³ Nogales, 4 January: 17.3 µg/m³ Nogales, 5 January: no reading Carson Carson, 26 December: 14.8 µg/m³ Carson, 27 December: 14.4 µg/m³ Carson, 28 December: 21.0 µg/m³ Carson, 29 December: 22.9 µg/m³ Carson, 30 December: 25.0 µg/m³ Carson, 31 December: 38.8 µg/m³, 2.9× its usual 13.4 Carson, 1 January: 28.7 µg/m³, 2.3× its usual 12.5 Carson, 2 January: 28.7 µg/m³, 2.4× its usual 11.8 Carson, 3 January: 24.1 µg/m³ Carson, 4 January: 20.6 µg/m³ Carson, 5 January: 19.4 µg/m³ Lomita Lomita, 26 December: 8.6 µg/m³ Lomita, 27 December: 10.9 µg/m³ Lomita, 28 December: 16.9 µg/m³ Lomita, 29 December: 21.1 µg/m³ Lomita, 30 December: 24.7 µg/m³ Lomita, 31 December: 34.3 µg/m³, 4.3× its usual 7.9 Lomita, 1 January: 21.3 µg/m³ Lomita, 2 January: 22.5 µg/m³ Lomita, 3 January: 20.6 µg/m³ Lomita, 4 January: 13.5 µg/m³ Lomita, 5 January: 10.9 µg/m³ Hawthorne Hawthorne, 26 December: 18.7 µg/m³ Hawthorne, 27 December: 16.5 µg/m³ Hawthorne, 28 December: 22.8 µg/m³ Hawthorne, 29 December: 22.2 µg/m³ Hawthorne, 30 December: 24.7 µg/m³ Hawthorne, 31 December: 33.0 µg/m³, 2.2× its usual 15.2 Hawthorne, 1 January: 28.3 µg/m³, 2.0× its usual 14.1 Hawthorne, 2 January: 27.1 µg/m³ Hawthorne, 3 January: 22.5 µg/m³ Hawthorne, 4 January: 21.6 µg/m³ Hawthorne, 5 January: 19.1 µg/m³ Torrance Torrance, 26 December: 13.0 µg/m³ Torrance, 27 December: 12.2 µg/m³ Torrance, 28 December: 19.7 µg/m³ Torrance, 29 December: 20.6 µg/m³ Torrance, 30 December: 24.2 µg/m³ Torrance, 31 December: 31.8 µg/m³, 2.7× its usual 11.6 Torrance, 1 January: 22.6 µg/m³ Torrance, 2 January: 24.5 µg/m³ Torrance, 3 January: 21.8 µg/m³ Torrance, 4 January: 16.9 µg/m³ Torrance, 5 January: 15.5 µg/m³ Mesa Mesa, 26 December: 11.8 µg/m³ Mesa, 27 December: 11.7 µg/m³ Mesa, 28 December: 15.6 µg/m³ Mesa, 29 December: 19.8 µg/m³ Mesa, 30 December: 16.7 µg/m³ Mesa, 31 December: 31.3 µg/m³, 3.9× its usual 8.1 Mesa, 1 January: 137.0 µg/m³, 17× its usual 8.2 Mesa, 2 January: 11.7 µg/m³ Mesa, 3 January: 15.0 µg/m³ Mesa, 4 January: 16.1 µg/m³ Mesa, 5 January: 12.3 µg/m³ Inglewood Inglewood, 26 December: 16.2 µg/m³ Inglewood, 27 December: 14.4 µg/m³ Inglewood, 28 December: 21.4 µg/m³ Inglewood, 29 December: 21.1 µg/m³ Inglewood, 30 December: 22.6 µg/m³ Inglewood, 31 December: 28.9 µg/m³, 2.7× its usual 10.7 Inglewood, 1 January: 24.5 µg/m³ Inglewood, 2 January: 20.9 µg/m³ Inglewood, 3 January: 21.9 µg/m³ Inglewood, 4 January: 20.3 µg/m³ Inglewood, 5 January: 14.5 µg/m³ Casa Grande Casa Grande, 26 December: 9.5 µg/m³ Casa Grande, 27 December: 13.0 µg/m³ Casa Grande, 28 December: 12.9 µg/m³ Casa Grande, 29 December: 15.6 µg/m³ Casa Grande, 30 December: 16.0 µg/m³ Casa Grande, 31 December: 28.7 µg/m³, 3.8× its usual 7.5 Casa Grande, 1 January: 29.5 µg/m³, 4.3× its usual 6.9 Casa Grande, 2 January: 15.6 µg/m³ Casa Grande, 3 January: 14.0 µg/m³ Casa Grande, 4 January: 15.9 µg/m³ Casa Grande, 5 January: 12.3 µg/m³ Tempe Tempe, 26 December: 11.6 µg/m³ Tempe, 27 December: 12.4 µg/m³ Tempe, 28 December: 11.4 µg/m³ Tempe, 29 December: 17.8 µg/m³ Tempe, 30 December: 14.0 µg/m³ Tempe, 31 December: 27.4 µg/m³, 3.2× its usual 8.6 Tempe, 1 January: 84.9 µg/m³, 9.9× its usual 8.6 Tempe, 2 January: 14.6 µg/m³ Tempe, 3 January: 13.1 µg/m³ Tempe, 4 January: 12.7 µg/m³ Tempe, 5 January: 13.9 µg/m³ Tijuana Tijuana, 26 December: 35.9 µg/m³ Tijuana, 27 December: 33.4 µg/m³ Tijuana, 28 December: 28.0 µg/m³ Tijuana, 29 December: 35.9 µg/m³ Tijuana, 30 December: 25.2 µg/m³ Tijuana, 31 December: 39.6 µg/m³ Tijuana, 1 January: 71.7 µg/m³, 2.5× its usual 29.1 Tijuana, 2 January: 39.2 µg/m³ Tijuana, 3 January: 36.9 µg/m³ Tijuana, 4 January: 37.3 µg/m³ Tijuana, 5 January: 33.3 µg/m³ Imperial Beach Imperial Beach, 26 December: 25.4 µg/m³ Imperial Beach, 27 December: 27.6 µg/m³ Imperial Beach, 28 December: 18.9 µg/m³ Imperial Beach, 29 December: 24.6 µg/m³ Imperial Beach, 30 December: 18.3 µg/m³ Imperial Beach, 31 December: 23.1 µg/m³ Imperial Beach, 1 January: 59.3 µg/m³, 3.4× its usual 17.5 Imperial Beach, 2 January: 48.2 µg/m³, 2.9× its usual 16.9 Imperial Beach, 3 January: 32.9 µg/m³ Imperial Beach, 4 January: 26.3 µg/m³ Imperial Beach, 5 January: 31.7 µg/m³ Chula Vista Chula Vista, 26 December: 13.3 µg/m³ Chula Vista, 27 December: 13.6 µg/m³ Chula Vista, 28 December: 10.7 µg/m³ Chula Vista, 29 December: 18.0 µg/m³ Chula Vista, 30 December: 12.4 µg/m³ Chula Vista, 31 December: 19.7 µg/m³ Chula Vista, 1 January: 48.7 µg/m³, 5.5× its usual 8.9 Chula Vista, 2 January: 22.5 µg/m³ Chula Vista, 3 January: 20.7 µg/m³ Chula Vista, 4 January: 16.9 µg/m³ Chula Vista, 5 January: 10.9 µg/m³ Nogales Nogales, 26 December: 18.9 µg/m³ Nogales, 27 December: 18.3 µg/m³ Nogales, 28 December: 19.9 µg/m³ Nogales, 29 December: 26.1 µg/m³ Nogales, 30 December: 19.8 µg/m³ Nogales, 31 December: 15.6 µg/m³ Nogales, 1 January: 45.6 µg/m³, 2.7× its usual 17.2 Nogales, 2 January: 23.2 µg/m³ Nogales, 3 January: 25.2 µg/m³ Nogales, 4 January: 11.3 µg/m³ Nogales, 5 January: 18.6 µg/m³ Fresno Fresno, 26 December: 12.8 µg/m³ Fresno, 27 December: 12.2 µg/m³ Fresno, 28 December: 18.3 µg/m³ Fresno, 29 December: 14.0 µg/m³ Fresno, 30 December: 9.3 µg/m³ Fresno, 31 December: 27.3 µg/m³ Fresno, 1 January: 43.0 µg/m³, 2.8× its usual 15.1 Fresno, 2 January: 33.4 µg/m³, 2.2× its usual 15.1 Fresno, 3 January: 23.3 µg/m³ Fresno, 4 January: 11.7 µg/m³ Fresno, 5 January: 20.0 µg/m³ Tucson Tucson, 26 December: 9.3 µg/m³ Tucson, 27 December: 9.0 µg/m³ Tucson, 28 December: 11.8 µg/m³ Tucson, 29 December: 10.8 µg/m³ Tucson, 30 December: 11.0 µg/m³ Tucson, 31 December: 16.1 µg/m³ Tucson, 1 January: 33.7 µg/m³, 4.3× its usual 7.9 Tucson, 2 January: 10.9 µg/m³ Tucson, 3 January: 11.6 µg/m³ Tucson, 4 January: 9.8 µg/m³ Tucson, 5 January: 9.0 µg/m³ El Cajon El Cajon, 26 December: 12.4 µg/m³ El Cajon, 27 December: 12.0 µg/m³ El Cajon, 28 December: 11.2 µg/m³ El Cajon, 29 December: 16.5 µg/m³ El Cajon, 30 December: 12.5 µg/m³ El Cajon, 31 December: 17.6 µg/m³ El Cajon, 1 January: 32.7 µg/m³, 3.4× its usual 9.7 El Cajon, 2 January: 16.4 µg/m³ El Cajon, 3 January: 20.2 µg/m³ El Cajon, 4 January: 17.2 µg/m³ El Cajon, 5 January: 12.8 µg/m³ San Diego San Diego, 26 December: 13.8 µg/m³ San Diego, 27 December: 12.0 µg/m³ San Diego, 28 December: 12.8 µg/m³ San Diego, 29 December: 21.6 µg/m³ San Diego, 30 December: 11.7 µg/m³ San Diego, 31 December: 16.1 µg/m³ San Diego, 1 January: 32.6 µg/m³, 3.6× its usual 9.1 San Diego, 2 January: 22.8 µg/m³ San Diego, 3 January: 26.6 µg/m³ San Diego, 4 January: 20.7 µg/m³ San Diego, 5 January: 12.8 µg/m³ Visalia Visalia, 26 December: 11.1 µg/m³ Visalia, 27 December: 14.9 µg/m³ Visalia, 28 December: 19.3 µg/m³ Visalia, 29 December: 15.3 µg/m³ Visalia, 30 December: 8.1 µg/m³ Visalia, 31 December: 18.7 µg/m³ Visalia, 1 January: 32.3 µg/m³, 2.3× its usual 14.1 Visalia, 2 January: 29.2 µg/m³, 2.1× its usual 14.1 Visalia, 3 January: 19.8 µg/m³ Visalia, 4 January: 15.9 µg/m³ Visalia, 5 January: 17.8 µg/m³ Marana Marana, 26 December: 10.2 µg/m³ Marana, 27 December: 10.8 µg/m³ Marana, 28 December: no reading Marana, 29 December: no reading Marana, 30 December: no reading Marana, 31 December: 23.4 µg/m³ Marana, 1 January: 31.3 µg/m³, 4.5× its usual 7.0 Marana, 2 January: 12.5 µg/m³ Marana, 3 January: 12.0 µg/m³ Marana, 4 January: 13.9 µg/m³ Marana, 5 January: 12.8 µg/m³ Vallejo Vallejo, 26 December: 6.2 µg/m³ Vallejo, 27 December: 8.1 µg/m³ Vallejo, 28 December: no reading Vallejo, 29 December: no reading Vallejo, 30 December: no reading Vallejo, 31 December: no reading Vallejo, 1 January: 28.7 µg/m³, 3.8× its usual 7.5 Vallejo, 2 January: 7.7 µg/m³ Vallejo, 3 January: 10.5 µg/m³ Vallejo, 4 January: 10.7 µg/m³ Vallejo, 5 January: 12.6 µg/m³ Madera Madera, 26 December: 10.0 µg/m³ Madera, 27 December: 11.4 µg/m³ Madera, 28 December: 10.1 µg/m³ Madera, 29 December: 9.8 µg/m³ Madera, 30 December: 6.6 µg/m³ Madera, 31 December: 17.4 µg/m³ Madera, 1 January: 27.8 µg/m³, 2.4× its usual 11.5 Madera, 2 January: 13.8 µg/m³ Madera, 3 January: 19.1 µg/m³ Madera, 4 January: 8.3 µg/m³ Madera, 5 January: 11.3 µg/m³ Oceanside Oceanside, 26 December: 10.3 µg/m³ Oceanside, 27 December: 9.5 µg/m³ Oceanside, 28 December: 13.5 µg/m³ Oceanside, 29 December: 19.9 µg/m³ Oceanside, 30 December: 12.1 µg/m³ Oceanside, 31 December: 12.1 µg/m³ Oceanside, 1 January: 27.6 µg/m³, 3.9× its usual 7.1 Oceanside, 2 January: 19.9 µg/m³ Oceanside, 3 January: 17.0 µg/m³ Oceanside, 4 January: 15.1 µg/m³ Oceanside, 5 January: 18.3 µg/m³ Stockton Stockton, 26 December: 8.7 µg/m³ Stockton, 27 December: 12.3 µg/m³ Stockton, 28 December: 19.5 µg/m³ Stockton, 29 December: 5.9 µg/m³ Stockton, 30 December: 6.1 µg/m³ Stockton, 31 December: 16.9 µg/m³ Stockton, 1 January: 26.6 µg/m³, 2.3× its usual 11.5 Stockton, 2 January: 15.8 µg/m³ Stockton, 3 January: 18.6 µg/m³ Stockton, 4 January: 11.8 µg/m³ Stockton, 5 January: 12.7 µg/m³ Las Vegas Las Vegas, 26 December: 9.0 µg/m³ Las Vegas, 27 December: 12.9 µg/m³ Las Vegas, 28 December: 16.9 µg/m³ Las Vegas, 29 December: 16.9 µg/m³ Las Vegas, 30 December: 10.1 µg/m³ Las Vegas, 31 December: 15.5 µg/m³ Las Vegas, 1 January: 26.2 µg/m³, 2.1× its usual 12.7 Las Vegas, 2 January: 14.8 µg/m³ Las Vegas, 3 January: 16.7 µg/m³ Las Vegas, 4 January: 5.4 µg/m³ Las Vegas, 5 January: 8.8 µg/m³ Modesto Modesto, 26 December: 9.4 µg/m³ Modesto, 27 December: 11.1 µg/m³ Modesto, 28 December: 14.4 µg/m³ Modesto, 29 December: 4.7 µg/m³ Modesto, 30 December: 3.2 µg/m³ Modesto, 31 December: 6.6 µg/m³ Modesto, 1 January: 26.0 µg/m³, 2.1× its usual 12.1 Modesto, 2 January: 19.1 µg/m³ Modesto, 3 January: 21.1 µg/m³ Modesto, 4 January: 9.1 µg/m³ Modesto, 5 January: 13.2 µg/m³ Clovis Clovis, 26 December: 12.0 µg/m³ Clovis, 27 December: 8.9 µg/m³ Clovis, 28 December: 12.7 µg/m³ Clovis, 29 December: 12.0 µg/m³ Clovis, 30 December: 7.3 µg/m³ Clovis, 31 December: 15.0 µg/m³ Clovis, 1 January: 25.7 µg/m³, 2.5× its usual 10.2 Clovis, 2 January: 19.8 µg/m³ Clovis, 3 January: 17.4 µg/m³ Clovis, 4 January: 11.1 µg/m³ Clovis, 5 January: 13.2 µg/m³ 26 Dec 28 30 1 Jan 3 5 Every counted city, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more. Good 0–50
Moderate 51–100
Sensitive groups 101–150
Unhealthy 151–200
Very unhealthy 201–300
Hazardous 301+
Every city it reached
City Days Highest Usual Above usual
Mesa Arizona, United States 2 1 January 8.2 17× Phoenix Arizona, United States 2 1 January 16.6 10× Tempe Arizona, United States 2 1 January 8.6 9.9× Glendale Arizona, United States 2 1 January 9.6 7.6× Nogales Arizona, United States 2 1 January 16.9 7.0× Jurupa Valley California, United States 5 1 January 12.4 6.1× Chula Vista California, United States 1 1 January 8.9 5.5× Riverside California, United States 4 1 January 9.8 4.9× Burbank California, United States 3 1 January 10.5 4.8× Anaheim California, United States 4 1 January 10.8 4.7× Marana Arizona, United States 1 1 January 7.0 4.5× Lomita California, United States 1 31 December 7.9 4.3× Tucson Arizona, United States 1 1 January 7.9 4.3× Casa Grande Arizona, United States 2 1 January 6.9 4.3× Oceanside California, United States 1 1 January 7.1 3.9× Vallejo California, United States 1 1 January 7.5 3.8× Long Beach California, United States 3 1 January 12.0 3.7× Fontana California, United States 4 31 December 9.8 3.7× San Diego California, United States 1 1 January 9.1 3.6× Imperial Beach California, United States 2 1 January 17.5 3.4× Calexico California, United States 2 31 December 13.1 3.4× El Cajon California, United States 1 1 January 9.7 3.4× Compton California, United States 3 1 January 16.0 3.2× Los Angeles California, United States 3 1 January 10.7 3.1× Carson California, United States 3 31 December 13.4 2.9× Fresno California, United States 2 1 January 15.1 2.8× Nogales Sonora, Mexico 1 1 January 17.2 2.7× Torrance California, United States 1 31 December 11.6 2.7× Inglewood California, United States 1 31 December 10.7 2.7× Tijuana Baja California, Mexico 1 1 January 29.1 2.5× Clovis California, United States 1 1 January 10.2 2.5× Madera California, United States 1 1 January 11.5 2.4× Visalia California, United States 2 1 January 14.1 2.3× Stockton California, United States 1 1 January 11.5 2.3× Hawthorne California, United States 2 31 December 15.2 2.2× Las Vegas Nevada, United States 1 1 January 12.7 2.1× Modesto California, United States 1 1 January 12.1 2.1×
Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.
Against other episodes in the United States and Mexico
Number 25 of 141 episodes in the United States and Mexico since our records began, by cities reached.
Eastern United States and Canada, 25 June to 2 July 2023 280 North-eastern United States and Canada, July 2026 264 Eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, 30 July to 9 August 2025 241 Eastern United States and Canada, July 2023 240 North-eastern United States and Canada, 3 to 9 June 2025 196 Eastern United States and Canada, 14 to 19 June 2023 161 North-eastern United States and Canada, 12 to 16 July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, 10 to 14 June 2025 104 North-western United States and Canada, 4 to 11 August 2026 99 North-eastern United States and Canada, 14 to 19 February 2026 96 South-western United States and Mexico, December 2024 to January 2025 37 Bars: cities reached; colour: the level of the episode's highest daily reading. All 141 .
Use this page SmogRank, South-western United States and Mexico, December 2024 to January 2025: 37 cities with PM2.5 at twice their usual or more, 29 December 2024 to 2 January 2025, smogrank.com/episodes/2024-12-south-western-united-states-and-mexico (accessed 4 October 2026).
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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms .
An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes . Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.
