SmogRank / Episodes / United States
California, United States, March 2026
For 4 days, from 20 to 23 March 2026, 11 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was South Lake Tahoe, California, United States: 40.3 µg/m³ on 20 March, about 5.9× its usual 6.8.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 11 in 1 country
Days 4 20 to 23 March 2026
Worst day 20 March 6 cities counted
Furthest above usual 5.9× South Lake Tahoe
Day by day
Play 20 March 6 cities at twice their usual or more
Corcoran Clovis Fresno Madera Ridgecrest Merced Atascadero Los Banos Lancaster San Luis Obispo Nipomo Arroyo Grande Fillmore Orcutt Turlock Santa Clarita Santa Barbara Goleta Simi Valley Oxnard Lompoc Thousand Oaks Modesto Agoura La Crescenta-Montrose Burbank Hollister Santa Monica Manteca Gilroy Glendora Victorville Salinas Prunedale Whittier Compton Torrance Stockton Tracy Carson Watsonville Lomita Seaside Long Beach Carson City Anaheim Fontana Jurupa Valley Galt Huntington Beach Live Oak San Jose Livermore Riverside Santa Cruz Elk Grove Pleasanton Folsom Truckee Sunnyvale Florin Fremont Mission Viejo Mountain View Arden-Arcade Roseville Palo Alto Sacramento Lake Elsinore Banning Lincoln Redwood City Concord San Leandro Davis San Mateo Martinez Oakland Vacaville Berkeley Woodland South San Francisco Vallejo Richmond San Francisco Yuba City Summerlin South San Rafael Spring Valley Enterprise Indio Las Vegas Henderson Santa Rosa Boulder City Windsor Ukiah Los Angeles Delano Tulare Hawthorne Inglewood Visalia Hanford Bakersfield Porterville Pasadena South Lake Tahoe 17 Mar 18 19 20 21 22 23 24 25 26 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
South Lake Tahoe South Lake Tahoe, 17 March: 41.2 µg/m³, 6.1× usual South Lake Tahoe, 18 March: 36.8 µg/m³, 5.4× usual South Lake Tahoe, 19 March: 39.3 µg/m³, 5.8× usual South Lake Tahoe, 20 March: 40.3 µg/m³, 5.9× usual South Lake Tahoe, 21 March: 38.8 µg/m³, 5.7× usual South Lake Tahoe, 22 March: 38.7 µg/m³, 5.7× usual South Lake Tahoe, 23 March: 24.8 µg/m³, 3.6× usual South Lake Tahoe, 24 March: 6.2 µg/m³, 0.9× usual South Lake Tahoe, 25 March: 5.9 µg/m³, 0.9× usual South Lake Tahoe, 26 March: 4.9 µg/m³, 0.7× usual Tulare Tulare, 17 March: 34.8 µg/m³, 3.6× usual Tulare, 18 March: 36.5 µg/m³, 3.8× usual Tulare, 19 March: 32.3 µg/m³, 3.4× usual Tulare, 20 March: 28.0 µg/m³, 2.9× usual Tulare, 21 March: 35.4 µg/m³, 3.7× usual Tulare, 22 March: 18.3 µg/m³, 1.9× usual Tulare, 23 March: 23.7 µg/m³, 2.5× usual Tulare, 24 March: 4.8 µg/m³, 0.5× usual Tulare, 25 March: 13.3 µg/m³, 1.4× usual Tulare, 26 March: 1.6 µg/m³, 0.2× usual Delano Delano, 17 March: 34.3 µg/m³, 2.9× usual Delano, 18 March: 39.7 µg/m³, 3.3× usual Delano, 19 March: 33.7 µg/m³, 2.8× usual Delano, 20 March: 38.7 µg/m³, 3.2× usual Delano, 21 March: 37.0 µg/m³, 3.1× usual Delano, 22 March: 27.4 µg/m³, 2.3× usual Delano, 23 March: 22.7 µg/m³, 1.9× usual Delano, 24 March: 12.9 µg/m³, 1.1× usual Delano, 25 March: 15.8 µg/m³, 1.3× usual Delano, 26 March: 8.8 µg/m³, 0.7× usual Porterville Porterville, 17 March: 19.1 µg/m³, 3.1× usual Porterville, 18 March: 22.0 µg/m³, 3.5× usual Porterville, 19 March: 21.0 µg/m³, 3.4× usual Porterville, 20 March: 33.8 µg/m³, 5.5× usual Porterville, 21 March: 28.0 µg/m³, 4.5× usual Porterville, 22 March: 26.2 µg/m³, 4.2× usual Porterville, 23 March: 27.0 µg/m³, 4.4× usual Porterville, 24 March: 18.7 µg/m³, 3.0× usual Porterville, 25 March: 15.8 µg/m³, 2.5× usual Porterville, 26 March: 16.0 µg/m³, 2.6× usual Visalia Visalia, 17 March: 20.5 µg/m³, 3.2× usual Visalia, 18 March: 21.2 µg/m³, 3.3× usual Visalia, 19 March: 19.9 µg/m³, 3.1× usual Visalia, 20 March: 27.4 µg/m³, 4.2× usual Visalia, 21 March: 26.0 µg/m³, 4.0× usual Visalia, 22 March: 15.9 µg/m³, 2.4× usual Visalia, 23 March: 19.7 µg/m³, 3.0× usual Visalia, 24 March: 11.5 µg/m³, 1.8× usual Visalia, 25 March: 19.0 µg/m³, 2.9× usual Visalia, 26 March: 9.7 µg/m³, 1.5× usual Bakersfield Bakersfield, 17 March: 21.0 µg/m³, 3.5× usual Bakersfield, 18 March: 24.1 µg/m³, 4.0× usual Bakersfield, 19 March: 23.7 µg/m³, 3.9× usual Bakersfield, 20 March: 27.1 µg/m³, 4.5× usual Bakersfield, 21 March: 22.8 µg/m³, 3.8× usual Bakersfield, 22 March: 18.6 µg/m³, 3.1× usual Bakersfield, 23 March: 13.9 µg/m³, 2.3× usual Bakersfield, 24 March: 11.6 µg/m³, 1.9× usual Bakersfield, 25 March: 12.0 µg/m³, 2.0× usual Bakersfield, 26 March: 10.3 µg/m³, 1.7× usual Hanford Hanford, 17 March: 18.4 µg/m³, 3.1× usual Hanford, 18 March: 19.9 µg/m³, 3.3× usual Hanford, 19 March: 16.9 µg/m³, 2.8× usual Hanford, 20 March: 14.4 µg/m³, 2.4× usual Hanford, 21 March: 25.8 µg/m³, 4.3× usual Hanford, 22 March: 9.8 µg/m³, 1.6× usual Hanford, 23 March: 7.4 µg/m³, 1.2× usual Hanford, 24 March: 8.7 µg/m³, 1.5× usual Hanford, 25 March: 6.9 µg/m³, 1.2× usual Hanford, 26 March: 5.2 µg/m³, 0.9× usual Pasadena Pasadena, 17 March: 0.5 µg/m³, 0.1× usual Pasadena, 18 March: 3.8 µg/m³, 0.5× usual Pasadena, 19 March: 11.1 µg/m³, 1.6× usual Pasadena, 20 March: 8.9 µg/m³, 1.3× usual Pasadena, 21 March: 15.4 µg/m³, 2.2× usual Pasadena, 22 March: 32.7 µg/m³, 4.7× usual Pasadena, 23 March: 39.8 µg/m³, 5.7× usual Pasadena, 24 March: 31.7 µg/m³, 4.5× usual Pasadena, 25 March: 30.9 µg/m³, 4.4× usual Pasadena, 26 March: 23.1 µg/m³, 3.3× usual Hawthorne Hawthorne, 17 March: 11.6 µg/m³, 1.6× usual Hawthorne, 18 March: 12.3 µg/m³, 1.7× usual Hawthorne, 19 March: 13.6 µg/m³, 1.9× usual Hawthorne, 20 March: 15.2 µg/m³, 2.1× usual Hawthorne, 21 March: 14.8 µg/m³, 2.1× usual Hawthorne, 22 March: 24.8 µg/m³, 3.5× usual Hawthorne, 23 March: 28.3 µg/m³, 4.0× usual Hawthorne, 24 March: 18.4 µg/m³, 2.6× usual Hawthorne, 25 March: 19.8 µg/m³, 2.8× usual Hawthorne, 26 March: 22.0 µg/m³, 3.1× usual Inglewood Inglewood, 17 March: 10.6 µg/m³, 1.6× usual Inglewood, 18 March: 12.0 µg/m³, 1.8× usual Inglewood, 19 March: 13.4 µg/m³, 2.0× usual Inglewood, 20 March: 16.2 µg/m³, 2.5× usual Inglewood, 21 March: 14.1 µg/m³, 2.1× usual Inglewood, 22 March: 24.0 µg/m³, 3.6× usual Inglewood, 23 March: 27.5 µg/m³, 4.2× usual Inglewood, 24 March: 18.6 µg/m³, 2.8× usual Inglewood, 25 March: 18.6 µg/m³, 2.8× usual Inglewood, 26 March: 21.1 µg/m³, 3.2× usual Los Angeles Los Angeles, 17 March: 10.2 µg/m³, 1.2× usual Los Angeles, 18 March: 14.0 µg/m³, 1.6× usual Los Angeles, 19 March: 15.5 µg/m³, 1.8× usual Los Angeles, 20 March: 16.2 µg/m³, 1.8× usual Los Angeles, 21 March: 15.0 µg/m³, 1.7× usual Los Angeles, 22 March: 20.6 µg/m³, 2.3× usual Los Angeles, 23 March: 26.3 µg/m³, 3.0× usual Los Angeles, 24 March: 17.1 µg/m³, 1.9× usual Los Angeles, 25 March: 18.0 µg/m³, 2.0× usual Los Angeles, 26 March: 14.8 µg/m³, 1.7× usual 17 Mar 18 19 20 21 22 23 24 25 26 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
South Lake Tahoe California, United States 3 17 March 6.8 6.1× Pasadena California, United States 2 23 March 7.0 5.7× Porterville California, United States 4 20 March 6.2 5.5× Bakersfield California, United States 1 20 March 6.0 4.5× Hanford California, United States 1 21 March 6.0 4.3× Visalia California, United States 2 20 March 6.5 4.2× Inglewood California, United States 1 23 March 6.6 4.2× Hawthorne California, United States 1 23 March 7.1 4.0× Tulare California, United States 2 18 March 9.6 3.8× Delano California, United States 3 18 March 12.0 3.3× Los Angeles California, United States 1 23 March 8.8 3.0×
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 66 of 98 episodes in the United States 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 California, United States, March 2026 11 Bars: cities reached; colour: the level of the episode's highest daily reading. All 98 .
Use this page SmogRank, California, United States, March 2026: 11 cities with PM2.5 at twice their usual or more, 20 to 23 March 2026, smogrank.com/episodes/2026-03-california-united-states (accessed 2 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.
