SmogRank / Episodes / United States
South-western United States, January 2025
For 2 days, from 1 to 2 January 2025, 33 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.
Likely New Year fireworks It came on the night of 31 December, when smoke from fireworks often fills the air over many cities at once.
Cities reached 33 in 2 countries
Days 2 1 to 2 January 2025
Worst day 1 January 33 cities counted
Furthest above usual 17× Mesa
Day by day
Play 1 January 33 cities at twice their usual or more
Victorville Banning Indio Lake Elsinore Temecula Glendora Ridgecrest Lancaster La Crescenta-Montrose Poway Enterprise Summerlin South Inglewood Spring Valley Lomita Torrance 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 Hawthorne Las Vegas Modesto Visalia Stockton Carson Madera Clovis Nogales Fresno Calexico Los Angeles Fontana Compton Tijuana El Cajon San Diego Long Beach Vallejo Oceanside Tucson Casa Grande Marana Anaheim Burbank Riverside Chula Vista Jurupa Valley Nogales Glendale Tempe Phoenix Mesa 29 Dec 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
Phoenix Phoenix, 29 December: 23.1 µg/m³, 1.4× usual Phoenix, 30 December: 22.5 µg/m³, 1.4× usual Phoenix, 31 December: 45.3 µg/m³, 2.7× usual Phoenix, 1 January: 167.0 µg/m³, 10× usual Phoenix, 2 January: 25.1 µg/m³, 1.5× usual Phoenix, 3 January: 22.1 µg/m³, 1.3× usual Phoenix, 4 January: 19.4 µg/m³, 1.2× usual Phoenix, 5 January: 19.0 µg/m³, 1.1× usual Mesa Mesa, 29 December: 19.8 µg/m³, 2.4× usual Mesa, 30 December: 16.7 µg/m³, 2.0× usual Mesa, 31 December: 31.3 µg/m³, 3.8× usual Mesa, 1 January: 137.0 µg/m³, 17× usual Mesa, 2 January: 11.7 µg/m³, 1.4× usual Mesa, 3 January: 15.0 µg/m³, 1.8× usual Mesa, 4 January: 16.1 µg/m³, 2.0× usual Mesa, 5 January: 12.3 µg/m³, 1.5× usual Nogales Nogales, 29 December: 21.7 µg/m³, 1.3× usual Nogales, 30 December: 23.8 µg/m³, 1.4× usual Nogales, 31 December: 40.3 µg/m³, 2.4× usual Nogales, 1 January: 118.0 µg/m³, 7.0× usual Nogales, 2 January: 25.2 µg/m³, 1.5× usual Nogales, 3 January: 23.1 µg/m³, 1.4× usual Nogales, 4 January: 17.3 µg/m³, 1.0× usual Nogales, 5 January: no reading Tempe Tempe, 29 December: 17.8 µg/m³, 2.1× usual Tempe, 30 December: 14.0 µg/m³, 1.6× usual Tempe, 31 December: 27.4 µg/m³, 3.2× usual Tempe, 1 January: 84.9 µg/m³, 9.9× usual Tempe, 2 January: 14.6 µg/m³, 1.7× usual Tempe, 3 January: 13.1 µg/m³, 1.5× usual Tempe, 4 January: 12.7 µg/m³, 1.5× usual Tempe, 5 January: 13.9 µg/m³, 1.6× usual Jurupa Valley Jurupa Valley, 29 December: 45.5 µg/m³, 3.7× usual Jurupa Valley, 30 December: 38.7 µg/m³, 3.1× usual Jurupa Valley, 31 December: 42.6 µg/m³, 3.4× usual Jurupa Valley, 1 January: 75.4 µg/m³, 6.1× usual Jurupa Valley, 2 January: 33.1 µg/m³, 2.7× usual Jurupa Valley, 3 January: 24.7 µg/m³, 2.0× usual Jurupa Valley, 4 January: 44.1 µg/m³, 3.6× usual Jurupa Valley, 5 January: 24.4 µg/m³, 2.0× usual Glendale Glendale, 29 December: 16.3 µg/m³, 1.7× usual Glendale, 30 December: 14.0 µg/m³, 1.5× usual Glendale, 31 December: 40.7 µg/m³, 4.2× usual Glendale, 1 January: 72.9 µg/m³, 7.6× usual Glendale, 2 January: 14.5 µg/m³, 1.5× usual Glendale, 3 January: 14.5 µg/m³, 1.5× usual Glendale, 4 January: 14.1 µg/m³, 1.5× usual Glendale, 5 January: 14.8 µg/m³, 1.5× usual Tijuana Tijuana, 29 December: 24.6 µg/m³, 1.3× usual Tijuana, 30 December: 18.3 µg/m³, 0.9× usual Tijuana, 31 December: 24.7 µg/m³, 1.3× usual Tijuana, 1 January: 62.1 µg/m³, 3.2× usual Tijuana, 2 January: 39.2 µg/m³, 2.0× usual Tijuana, 3 January: 32.9 µg/m³, 1.7× usual Tijuana, 4 January: 26.3 µg/m³, 1.4× usual Tijuana, 5 January: 31.7 µg/m³, 1.6× usual Anaheim Anaheim, 29 December: 40.0 µg/m³, 3.7× usual Anaheim, 30 December: 23.2 µg/m³, 2.1× usual Anaheim, 31 December: 42.4 µg/m³, 3.9× usual Anaheim, 1 January: 51.0 µg/m³, 4.7× usual Anaheim, 2 January: 33.0 µg/m³, 3.1× usual Anaheim, 3 January: 22.4 µg/m³, 2.1× usual Anaheim, 4 January: 21.7 µg/m³, 2.0× usual Anaheim, 5 January: 21.5 µg/m³, 2.0× usual Compton Compton, 29 December: 27.3 µg/m³, 1.7× usual Compton, 30 December: 23.5 µg/m³, 1.5× usual Compton, 31 December: 46.0 µg/m³, 2.9× usual Compton, 1 January: 50.9 µg/m³, 3.2× usual Compton, 2 January: 32.2 µg/m³, 2.0× usual Compton, 3 January: 22.0 µg/m³, 1.4× usual Compton, 4 January: 25.3 µg/m³, 1.6× usual Compton, 5 January: 23.7 µg/m³, 1.5× usual Burbank Burbank, 29 December: 24.2 µg/m³, 2.3× usual Burbank, 30 December: 31.5 µg/m³, 3.0× usual Burbank, 31 December: 30.9 µg/m³, 2.9× usual Burbank, 1 January: 50.1 µg/m³, 4.8× usual Burbank, 2 January: 21.1 µg/m³, 2.0× usual Burbank, 3 January: 21.4 µg/m³, 2.0× usual Burbank, 4 January: 31.3 µg/m³, 3.0× usual Burbank, 5 January: 11.6 µg/m³, 1.1× usual Chula Vista Chula Vista, 29 December: 18.0 µg/m³, 2.0× usual Chula Vista, 30 December: 12.4 µg/m³, 1.4× usual Chula Vista, 31 December: 19.7 µg/m³, 2.2× usual Chula Vista, 1 January: 48.7 µg/m³, 5.5× usual Chula Vista, 2 January: 22.5 µg/m³, 2.5× usual Chula Vista, 3 January: 20.7 µg/m³, 2.3× usual Chula Vista, 4 January: 16.9 µg/m³, 1.9× usual Chula Vista, 5 January: 10.9 µg/m³, 1.2× usual Riverside Riverside, 29 December: 36.9 µg/m³, 3.8× usual Riverside, 30 December: 34.9 µg/m³, 3.6× usual Riverside, 31 December: 34.9 µg/m³, 3.6× usual Riverside, 1 January: 48.5 µg/m³, 4.9× usual Riverside, 2 January: 17.6 µg/m³, 1.8× usual Riverside, 3 January: 18.5 µg/m³, 1.9× usual Riverside, 4 January: 40.5 µg/m³, 4.1× usual Riverside, 5 January: 12.7 µg/m³, 1.3× usual Nogales Nogales, 29 December: 26.1 µg/m³, 1.5× usual Nogales, 30 December: 19.8 µg/m³, 1.2× usual Nogales, 31 December: 15.6 µg/m³, 0.9× usual Nogales, 1 January: 45.6 µg/m³, 2.7× usual Nogales, 2 January: 23.2 µg/m³, 1.3× usual Nogales, 3 January: 25.2 µg/m³, 1.5× usual Nogales, 4 January: 11.3 µg/m³, 0.7× usual Nogales, 5 January: 18.6 µg/m³, 1.1× usual Long Beach Long Beach, 29 December: 25.0 µg/m³, 2.1× usual Long Beach, 30 December: 19.9 µg/m³, 1.7× usual Long Beach, 31 December: 41.5 µg/m³, 3.5× usual Long Beach, 1 January: 43.9 µg/m³, 3.7× usual Long Beach, 2 January: 29.8 µg/m³, 2.5× usual Long Beach, 3 January: 21.8 µg/m³, 1.8× usual Long Beach, 4 January: 17.2 µg/m³, 1.4× usual Long Beach, 5 January: 23.2 µg/m³, 1.9× usual Fresno Fresno, 29 December: 14.0 µg/m³, 0.9× usual Fresno, 30 December: 9.3 µg/m³, 0.6× usual Fresno, 31 December: 27.3 µg/m³, 1.8× usual Fresno, 1 January: 43.0 µg/m³, 2.8× usual Fresno, 2 January: 33.4 µg/m³, 2.2× usual Fresno, 3 January: 23.3 µg/m³, 1.5× usual Fresno, 4 January: 11.7 µg/m³, 0.8× usual Fresno, 5 January: 20.0 µg/m³, 1.3× usual Calexico Calexico, 29 December: no reading Calexico, 30 December: no reading Calexico, 31 December: 44.1 µg/m³, 3.6× usual Calexico, 1 January: 37.0 µg/m³, 3.0× usual Calexico, 2 January: 12.7 µg/m³, 1.0× usual Calexico, 3 January: 18.4 µg/m³, 1.5× usual Calexico, 4 January: 22.0 µg/m³, 1.8× usual Calexico, 5 January: 8.5 µg/m³, 0.7× usual Tucson Tucson, 29 December: 10.8 µg/m³, 1.4× usual Tucson, 30 December: 11.0 µg/m³, 1.4× usual Tucson, 31 December: 16.1 µg/m³, 2.0× usual Tucson, 1 January: 33.7 µg/m³, 4.3× usual Tucson, 2 January: 10.9 µg/m³, 1.4× usual Tucson, 3 January: 11.6 µg/m³, 1.5× usual Tucson, 4 January: 9.8 µg/m³, 1.2× usual Tucson, 5 January: 9.0 µg/m³, 1.1× usual El Cajon El Cajon, 29 December: 16.5 µg/m³, 1.7× usual El Cajon, 30 December: 12.5 µg/m³, 1.3× usual El Cajon, 31 December: 17.6 µg/m³, 1.8× usual El Cajon, 1 January: 32.7 µg/m³, 3.4× usual El Cajon, 2 January: 16.4 µg/m³, 1.7× usual El Cajon, 3 January: 20.2 µg/m³, 2.1× usual El Cajon, 4 January: 17.2 µg/m³, 1.8× usual El Cajon, 5 January: 12.8 µg/m³, 1.3× usual Los Angeles Los Angeles, 29 December: 21.4 µg/m³, 2.0× usual Los Angeles, 30 December: 26.3 µg/m³, 2.5× usual Los Angeles, 31 December: 31.5 µg/m³, 2.9× usual Los Angeles, 1 January: 32.7 µg/m³, 3.1× usual Los Angeles, 2 January: 20.5 µg/m³, 1.9× usual Los Angeles, 3 January: 25.6 µg/m³, 2.4× usual Los Angeles, 4 January: 29.9 µg/m³, 2.8× usual Los Angeles, 5 January: 12.7 µg/m³, 1.2× usual San Diego San Diego, 29 December: 21.6 µg/m³, 2.4× usual San Diego, 30 December: 11.7 µg/m³, 1.3× usual San Diego, 31 December: 16.1 µg/m³, 1.8× usual San Diego, 1 January: 32.6 µg/m³, 3.6× usual San Diego, 2 January: 22.8 µg/m³, 2.5× usual San Diego, 3 January: 26.6 µg/m³, 2.9× usual San Diego, 4 January: 20.7 µg/m³, 2.3× usual San Diego, 5 January: 12.8 µg/m³, 1.4× usual Visalia Visalia, 29 December: 15.3 µg/m³, 1.1× usual Visalia, 30 December: 8.1 µg/m³, 0.6× usual Visalia, 31 December: 18.7 µg/m³, 1.3× usual Visalia, 1 January: 32.3 µg/m³, 2.3× usual Visalia, 2 January: 29.2 µg/m³, 2.1× usual Visalia, 3 January: 19.8 µg/m³, 1.4× usual Visalia, 4 January: 15.9 µg/m³, 1.1× usual Visalia, 5 January: 17.8 µg/m³, 1.3× usual Marana Marana, 29 December: no reading Marana, 30 December: no reading Marana, 31 December: 23.4 µg/m³, 3.3× usual Marana, 1 January: 31.3 µg/m³, 4.5× usual Marana, 2 January: 12.5 µg/m³, 1.8× usual Marana, 3 January: 12.0 µg/m³, 1.7× usual Marana, 4 January: 13.9 µg/m³, 2.0× usual Marana, 5 January: 12.8 µg/m³, 1.8× usual Fontana Fontana, 29 December: 27.3 µg/m³, 2.7× usual Fontana, 30 December: 32.6 µg/m³, 3.3× usual Fontana, 31 December: 36.5 µg/m³, 3.7× usual Fontana, 1 January: 30.5 µg/m³, 3.1× usual Fontana, 2 January: 14.0 µg/m³, 1.4× usual Fontana, 3 January: 19.7 µg/m³, 2.0× usual Fontana, 4 January: 38.7 µg/m³, 3.9× usual Fontana, 5 January: 12.4 µg/m³, 1.2× usual Casa Grande Casa Grande, 29 December: 15.6 µg/m³, 2.3× usual Casa Grande, 30 December: 16.0 µg/m³, 2.3× usual Casa Grande, 31 December: 28.7 µg/m³, 4.2× usual Casa Grande, 1 January: 29.5 µg/m³, 4.3× usual Casa Grande, 2 January: 15.6 µg/m³, 2.3× usual Casa Grande, 3 January: 14.0 µg/m³, 2.0× usual Casa Grande, 4 January: 15.9 µg/m³, 2.3× usual Casa Grande, 5 January: 12.3 µg/m³, 1.8× usual Vallejo Vallejo, 29 December: no reading Vallejo, 30 December: no reading Vallejo, 31 December: no reading Vallejo, 1 January: 28.7 µg/m³, 3.8× usual Vallejo, 2 January: 7.7 µg/m³, 1.0× usual Vallejo, 3 January: 10.5 µg/m³, 1.4× usual Vallejo, 4 January: 10.7 µg/m³, 1.4× usual Vallejo, 5 January: 12.6 µg/m³, 1.7× usual Carson Carson, 29 December: 22.9 µg/m³, 1.8× usual Carson, 30 December: 25.0 µg/m³, 2.0× usual Carson, 31 December: 38.8 µg/m³, 3.1× usual Carson, 1 January: 28.7 µg/m³, 2.3× usual Carson, 2 January: 28.7 µg/m³, 2.3× usual Carson, 3 January: 24.1 µg/m³, 1.9× usual Carson, 4 January: 20.6 µg/m³, 1.6× usual Carson, 5 January: 19.4 µg/m³, 1.6× usual Hawthorne Hawthorne, 29 December: 22.2 µg/m³, 1.6× usual Hawthorne, 30 December: 24.7 µg/m³, 1.8× usual Hawthorne, 31 December: 33.0 µg/m³, 2.3× usual Hawthorne, 1 January: 28.3 µg/m³, 2.0× usual Hawthorne, 2 January: 27.1 µg/m³, 1.9× usual Hawthorne, 3 January: 22.5 µg/m³, 1.6× usual Hawthorne, 4 January: 21.6 µg/m³, 1.5× usual Hawthorne, 5 January: 19.1 µg/m³, 1.4× usual Madera Madera, 29 December: 9.8 µg/m³, 0.9× usual Madera, 30 December: 6.6 µg/m³, 0.6× usual Madera, 31 December: 17.4 µg/m³, 1.5× usual Madera, 1 January: 27.8 µg/m³, 2.4× usual Madera, 2 January: 13.8 µg/m³, 1.2× usual Madera, 3 January: 19.1 µg/m³, 1.7× usual Madera, 4 January: 8.3 µg/m³, 0.7× usual Madera, 5 January: 11.3 µg/m³, 1.0× usual Oceanside Oceanside, 29 December: 19.9 µg/m³, 2.8× usual Oceanside, 30 December: 12.1 µg/m³, 1.7× usual Oceanside, 31 December: 12.1 µg/m³, 1.7× usual Oceanside, 1 January: 27.6 µg/m³, 3.9× usual Oceanside, 2 January: 19.9 µg/m³, 2.8× usual Oceanside, 3 January: 17.0 µg/m³, 2.4× usual Oceanside, 4 January: 15.1 µg/m³, 2.1× usual Oceanside, 5 January: 18.3 µg/m³, 2.6× usual Stockton Stockton, 29 December: 5.9 µg/m³, 0.5× usual Stockton, 30 December: 6.1 µg/m³, 0.5× usual Stockton, 31 December: 16.9 µg/m³, 1.5× usual Stockton, 1 January: 26.6 µg/m³, 2.3× usual Stockton, 2 January: 15.8 µg/m³, 1.4× usual Stockton, 3 January: 18.6 µg/m³, 1.6× usual Stockton, 4 January: 11.8 µg/m³, 1.0× usual Stockton, 5 January: 12.7 µg/m³, 1.1× usual Las Vegas Las Vegas, 29 December: 16.9 µg/m³, 1.3× usual Las Vegas, 30 December: 10.1 µg/m³, 0.8× usual Las Vegas, 31 December: 15.5 µg/m³, 1.2× usual Las Vegas, 1 January: 26.2 µg/m³, 2.1× usual Las Vegas, 2 January: 14.8 µg/m³, 1.2× usual Las Vegas, 3 January: 16.7 µg/m³, 1.3× usual Las Vegas, 4 January: 5.4 µg/m³, 0.4× usual Las Vegas, 5 January: 8.8 µg/m³, 0.7× usual Modesto Modesto, 29 December: 4.7 µg/m³, 0.4× usual Modesto, 30 December: 3.2 µg/m³, 0.3× usual Modesto, 31 December: 6.6 µg/m³, 0.5× usual Modesto, 1 January: 26.0 µg/m³, 2.1× usual Modesto, 2 January: 19.1 µg/m³, 1.6× usual Modesto, 3 January: 21.1 µg/m³, 1.7× usual Modesto, 4 January: 9.1 µg/m³, 0.8× usual Modesto, 5 January: 13.2 µg/m³, 1.1× usual Clovis Clovis, 29 December: 12.0 µg/m³, 1.2× usual Clovis, 30 December: 7.3 µg/m³, 0.7× usual Clovis, 31 December: 15.0 µg/m³, 1.5× usual Clovis, 1 January: 25.7 µg/m³, 2.5× usual Clovis, 2 January: 19.8 µg/m³, 1.9× usual Clovis, 3 January: 17.4 µg/m³, 1.7× usual Clovis, 4 January: 11.1 µg/m³, 1.1× usual Clovis, 5 January: 13.2 µg/m³, 1.3× usual 29 Dec 30 31 1 Jan 2 3 4 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 1 1 January 8.2 17× Phoenix Arizona, United States 1 1 January 16.6 10× Tempe Arizona, United States 1 1 January 8.6 9.9× Glendale Arizona, United States 1 1 January 9.6 7.6× Nogales Arizona, United States 1 1 January 16.9 7.0× Jurupa Valley California, United States 2 1 January 12.4 6.1× Chula Vista California, United States 1 1 January 8.9 5.5× Riverside California, United States 1 1 January 9.8 4.9× Burbank California, United States 1 1 January 10.5 4.8× Anaheim California, United States 2 1 January 10.8 4.7× Marana Arizona, United States 1 1 January 7.0 4.5× Casa Grande Arizona, United States 1 1 January 6.9 4.3× Tucson Arizona, United States 1 1 January 7.9 4.3× Oceanside California, United States 1 1 January 7.1 3.9× Fontana California, United States 1 4 January 10.0 3.9× Vallejo California, United States 1 1 January 7.5 3.8× Long Beach California, United States 2 1 January 12.0 3.7× Calexico California, United States 1 31 December 12.3 3.6× San Diego California, United States 1 1 January 9.1 3.6× El Cajon California, United States 1 1 January 9.7 3.4× Tijuana Baja California, Mexico 2 1 January 19.4 3.2× Compton California, United States 2 1 January 16.0 3.2× Carson California, United States 2 31 December 12.5 3.1× Los Angeles California, United States 1 1 January 10.7 3.1× Fresno California, United States 2 1 January 15.1 2.8× Nogales Sonora, Mexico 1 1 January 17.2 2.7× Clovis California, United States 1 1 January 10.2 2.5× Madera California, United States 1 1 January 11.5 2.4× Hawthorne California, United States 1 31 December 14.1 2.3× Stockton California, United States 1 1 January 11.5 2.3× Visalia California, United States 2 1 January 14.1 2.3× Modesto California, United States 1 1 January 12.1 2.1× Las Vegas Nevada, United States 1 1 January 12.7 2.1×
Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.
Against other episodes in the United States and Mexico
Number 24 of 106 episodes in the United States and Mexico since our records began, by cities reached.
North-eastern United States and Canada, June and July 2023 279 North-eastern United States and Canada, July 2026 264 North-eastern United States and Canada, May and June 2023 260 North-eastern United States and Canada, July and August 2025 241 North-eastern United States and Canada, July 2023 241 North-eastern United States and Canada, June 2025 196 North-eastern United States and Canada, June 2023 161 North-eastern United States and Canada, July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States, June 2025 104 North-western United States and Canada, August 2026 99 North-eastern United States and Canada, February 2026 96 South-western United States, January 2025 33 Bars: cities reached; colour: the level of the episode's highest daily reading. All 106 .
Use this page SmogRank, South-western United States, January 2025: 33 cities with PM2.5 at twice their usual or more, 1 to 2 January 2025, smogrank.com/episodes/2025-01-south-western-united-states (accessed 2 October 2026).
Copy citation Download top 10 (PNG)
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.
