SmogRank / Episodes / United States
California, United States, January 2024
For 3 days, from 15 to 17 January 2024, 12 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Lake Elsinore, California, United States: 36.3 µg/m³ on 17 January, about 6.7× its usual 5.4.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 12 in 1 country
Days 3 15 to 17 January 2024
Worst day 16 January 8 cities counted
Furthest above usual 6.7× Lake Elsinore
Day by day
Play 16 January 8 cities at twice their usual or more
Banning Victorville Indio Glendora Oceanside Lancaster Poway La Crescenta-Montrose Los Angeles Burbank Long Beach El Cajon Lomita San Diego Santa Monica Santa Clarita Chula Vista Imperial Beach Brawley Tijuana Agoura El Centro Simi Valley Thousand Oaks Fillmore Enterprise Summerlin South Mexicali Spring Valley Henderson Bakersfield Boulder City Yuma Porterville Santa Barbara Visalia Corcoran Hanford Mesquite Orcutt Lompoc Nipomo Clovis Fresno Arroyo Grande Atascadero Glendale Phoenix Tempe Mesa Hollister Salinas Compton Hawthorne Jurupa Valley Las Vegas Torrance Carson Anaheim Riverside Inglewood Calexico Fontana Lake Elsinore 12 Jan 13 14 15 16 17 18 19 20 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
Calexico Calexico, 12 January: 44.3 µg/m³, 4.2× usual Calexico, 13 January: 16.7 µg/m³, 1.6× usual Calexico, 14 January: no reading Calexico, 15 January: 22.4 µg/m³, 2.1× usual Calexico, 16 January: 13.3 µg/m³, 1.3× usual Calexico, 17 January: 36.2 µg/m³, 3.4× usual Calexico, 18 January: 23.9 µg/m³, 2.3× usual Calexico, 19 January: 21.2 µg/m³, 2.0× usual Calexico, 20 January: 33.7 µg/m³, 3.2× usual Jurupa Valley Jurupa Valley, 12 January: 13.3 µg/m³, 1.3× usual Jurupa Valley, 13 January: 19.6 µg/m³, 1.9× usual Jurupa Valley, 14 January: 29.2 µg/m³, 2.8× usual Jurupa Valley, 15 January: 28.7 µg/m³, 2.7× usual Jurupa Valley, 16 January: 28.5 µg/m³, 2.7× usual Jurupa Valley, 17 January: 25.8 µg/m³, 2.5× usual Jurupa Valley, 18 January: 19.8 µg/m³, 1.9× usual Jurupa Valley, 19 January: 18.6 µg/m³, 1.8× usual Jurupa Valley, 20 January: 20.5 µg/m³, 2.0× usual Riverside Riverside, 12 January: 10.0 µg/m³, 1.2× usual Riverside, 13 January: 18.7 µg/m³, 2.2× usual Riverside, 14 January: 26.4 µg/m³, 3.1× usual Riverside, 15 January: 27.7 µg/m³, 3.2× usual Riverside, 16 January: 25.8 µg/m³, 3.0× usual Riverside, 17 January: 28.4 µg/m³, 3.3× usual Riverside, 18 January: 19.3 µg/m³, 2.2× usual Riverside, 19 January: 17.0 µg/m³, 2.0× usual Riverside, 20 January: 15.5 µg/m³, 1.8× usual Hawthorne Hawthorne, 12 January: 7.9 µg/m³, 0.7× usual Hawthorne, 13 January: 14.3 µg/m³, 1.2× usual Hawthorne, 14 January: 22.1 µg/m³, 1.9× usual Hawthorne, 15 January: 29.6 µg/m³, 2.6× usual Hawthorne, 16 January: 29.7 µg/m³, 2.6× usual Hawthorne, 17 January: 21.2 µg/m³, 1.8× usual Hawthorne, 18 January: 17.9 µg/m³, 1.5× usual Hawthorne, 19 January: 18.1 µg/m³, 1.6× usual Hawthorne, 20 January: 11.2 µg/m³, 1.0× usual Carson Carson, 12 January: 7.8 µg/m³, 0.8× usual Carson, 13 January: 14.0 µg/m³, 1.4× usual Carson, 14 January: 23.7 µg/m³, 2.3× usual Carson, 15 January: 27.7 µg/m³, 2.7× usual Carson, 16 January: 30.3 µg/m³, 3.0× usual Carson, 17 January: 23.0 µg/m³, 2.3× usual Carson, 18 January: 14.8 µg/m³, 1.5× usual Carson, 19 January: 15.1 µg/m³, 1.5× usual Carson, 20 January: 11.2 µg/m³, 1.1× usual Las Vegas Las Vegas, 12 January: 12.1 µg/m³, 1.2× usual Las Vegas, 13 January: 11.6 µg/m³, 1.2× usual Las Vegas, 14 January: 15.5 µg/m³, 1.6× usual Las Vegas, 15 January: 27.5 µg/m³, 2.8× usual Las Vegas, 16 January: 19.1 µg/m³, 2.0× usual Las Vegas, 17 January: 16.9 µg/m³, 1.7× usual Las Vegas, 18 January: 19.3 µg/m³, 2.0× usual Las Vegas, 19 January: 18.8 µg/m³, 1.9× usual Las Vegas, 20 January: 22.9 µg/m³, 2.4× usual Inglewood Inglewood, 12 January: 6.4 µg/m³, 0.8× usual Inglewood, 13 January: 9.8 µg/m³, 1.2× usual Inglewood, 14 January: 15.8 µg/m³, 2.0× usual Inglewood, 15 January: 26.0 µg/m³, 3.3× usual Inglewood, 16 January: 26.0 µg/m³, 3.3× usual Inglewood, 17 January: 19.4 µg/m³, 2.4× usual Inglewood, 18 January: 18.2 µg/m³, 2.3× usual Inglewood, 19 January: 18.1 µg/m³, 2.3× usual Inglewood, 20 January: 9.1 µg/m³, 1.1× usual Torrance Torrance, 12 January: 8.8 µg/m³, 1.0× usual Torrance, 13 January: 12.8 µg/m³, 1.5× usual Torrance, 14 January: 18.5 µg/m³, 2.1× usual Torrance, 15 January: 25.4 µg/m³, 2.9× usual Torrance, 16 January: 26.6 µg/m³, 3.0× usual Torrance, 17 January: 21.6 µg/m³, 2.5× usual Torrance, 18 January: 16.0 µg/m³, 1.8× usual Torrance, 19 January: 16.0 µg/m³, 1.8× usual Torrance, 20 January: 10.2 µg/m³, 1.2× usual Compton Compton, 12 January: 12.8 µg/m³, 0.9× usual Compton, 13 January: 23.7 µg/m³, 1.7× usual Compton, 14 January: 22.9 µg/m³, 1.6× usual Compton, 15 January: 26.3 µg/m³, 1.9× usual Compton, 16 January: 27.8 µg/m³, 2.0× usual Compton, 17 January: 22.3 µg/m³, 1.6× usual Compton, 18 January: 15.8 µg/m³, 1.1× usual Compton, 19 January: 18.1 µg/m³, 1.3× usual Compton, 20 January: 13.5 µg/m³, 1.0× usual Anaheim Anaheim, 12 January: 9.3 µg/m³, 1.2× usual Anaheim, 13 January: 11.5 µg/m³, 1.5× usual Anaheim, 14 January: 12.4 µg/m³, 1.6× usual Anaheim, 15 January: 19.3 µg/m³, 2.4× usual Anaheim, 16 January: 25.4 µg/m³, 3.2× usual Anaheim, 17 January: no reading Anaheim, 18 January: no reading Anaheim, 19 January: no reading Anaheim, 20 January: no reading Lake Elsinore Lake Elsinore, 12 January: no reading Lake Elsinore, 13 January: no reading Lake Elsinore, 14 January: no reading Lake Elsinore, 15 January: no reading Lake Elsinore, 16 January: no reading Lake Elsinore, 17 January: 36.3 µg/m³, 6.7× usual Lake Elsinore, 18 January: 21.6 µg/m³, 4.0× usual Lake Elsinore, 19 January: 18.2 µg/m³, 3.4× usual Lake Elsinore, 20 January: 17.3 µg/m³, 3.2× usual Fontana Fontana, 12 January: 10.3 µg/m³, 1.5× usual Fontana, 13 January: 15.4 µg/m³, 2.2× usual Fontana, 14 January: 22.3 µg/m³, 3.1× usual Fontana, 15 January: 24.8 µg/m³, 3.5× usual Fontana, 16 January: 23.2 µg/m³, 3.3× usual Fontana, 17 January: 31.9 µg/m³, 4.5× usual Fontana, 18 January: 24.4 µg/m³, 3.4× usual Fontana, 19 January: 12.7 µg/m³, 1.8× usual Fontana, 20 January: 17.0 µg/m³, 2.4× usual 12 Jan 13 14 15 16 17 18 19 20 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
Lake Elsinore California, United States 1 17 January 5.4 6.7× Fontana California, United States 1 17 January 7.1 4.5× Calexico California, United States 1 12 January 10.6 4.2× Riverside California, United States 3 17 January 8.6 3.3× Inglewood California, United States 2 15 January 8.0 3.3× Anaheim California, United States 1 16 January 7.9 3.2× Torrance California, United States 2 16 January 8.8 3.0× Carson California, United States 2 16 January 10.2 3.0× Las Vegas Nevada, United States 1 15 January 9.7 2.8× Jurupa Valley California, United States 3 14 January 10.5 2.8× Hawthorne California, United States 2 16 January 11.6 2.6× Compton California, United States 1 16 January 13.9 2.0×
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
Number 87 of 131 episodes in the United States since our records began, by cities reached.
North-eastern United States and Canada, June and July 2023 280 North-eastern United States and Canada, July 2026 264 North-eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, July and August 2025 241 North-eastern United States and Canada, July 2023 240 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 California, United States, January 2024 12 Bars: cities reached; colour: the level of the episode's highest daily reading. All 131 .
Use this page SmogRank, California, United States, January 2024: 12 cities with PM2.5 at twice their usual or more, 15 to 17 January 2024, smogrank.com/episodes/2024-01-california-united-states (accessed 3 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.
