SmogRank / Episodes / United States

Utah, United States, November 2023

For 2 days, from 29 to 30 November 2023, 10 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Pocatello, Idaho, United States: 39.1 µg/m³ on 29 November, about 7.8× its usual 4.8.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached10in 1 country
Days229 to 30 November 2023
Worst day30 November8 cities counted
Furthest above usual7.8×Pocatello

Day by day

30 November 8 cities at twice their usual or more
North OgdenTooeleIdaho FallsTwin FallsRock SpringsGrand JunctionBoiseMeridianSalt Lake CityMillcreekMagnaBountifulWest JordanOremHighlandHerrimanSpanish ForkPocatello
26 Nov272829301 Dec23
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

MillcreekMillcreek, 26 November: 7.0 µg/m³, 0.7× usualMillcreek, 27 November: 18.6 µg/m³, 2.0× usualMillcreek, 28 November: 29.9 µg/m³, 3.2× usualMillcreek, 29 November: 34.6 µg/m³, 3.7× usualMillcreek, 30 November: 32.7 µg/m³, 3.5× usualMillcreek, 1 December: 22.2 µg/m³, 2.4× usualMillcreek, 2 December: 1.6 µg/m³, 0.2× usualMillcreek, 3 December: 4.5 µg/m³, 0.5× usualWest JordanWest Jordan, 26 November: 7.4 µg/m³, 1.0× usualWest Jordan, 27 November: 16.1 µg/m³, 2.1× usualWest Jordan, 28 November: 26.9 µg/m³, 3.5× usualWest Jordan, 29 November: 32.6 µg/m³, 4.3× usualWest Jordan, 30 November: 31.5 µg/m³, 4.1× usualWest Jordan, 1 December: 19.6 µg/m³, 2.6× usualWest Jordan, 2 December: 0.9 µg/m³, 0.1× usualWest Jordan, 3 December: 2.8 µg/m³, 0.4× usualPocatelloPocatello, 26 November: 4.8 µg/m³, 1.0× usualPocatello, 27 November: 7.7 µg/m³, 1.5× usualPocatello, 28 November: 17.1 µg/m³, 3.4× usualPocatello, 29 November: 39.1 µg/m³, 7.8× usualPocatello, 30 November: 23.2 µg/m³, 4.6× usualPocatello, 1 December: 7.9 µg/m³, 1.6× usualPocatello, 2 December: 1.5 µg/m³, 0.3× usualPocatello, 3 December: 2.0 µg/m³, 0.4× usualHerrimanHerriman, 26 November: 6.5 µg/m³, 1.3× usualHerriman, 27 November: 14.4 µg/m³, 2.9× usualHerriman, 28 November: 13.6 µg/m³, 2.7× usualHerriman, 29 November: 28.3 µg/m³, 5.7× usualHerriman, 30 November: 31.0 µg/m³, 6.2× usualHerriman, 1 December: 11.3 µg/m³, 2.3× usualHerriman, 2 December: 0.5 µg/m³, 0.1× usualHerriman, 3 December: 1.3 µg/m³, 0.3× usualSalt Lake CitySalt Lake City, 26 November: 5.3 µg/m³, 0.7× usualSalt Lake City, 27 November: 14.5 µg/m³, 1.8× usualSalt Lake City, 28 November: 23.5 µg/m³, 2.9× usualSalt Lake City, 29 November: 27.8 µg/m³, 3.5× usualSalt Lake City, 30 November: 28.3 µg/m³, 3.5× usualSalt Lake City, 1 December: 18.0 µg/m³, 2.3× usualSalt Lake City, 2 December: 2.0 µg/m³, 0.3× usualSalt Lake City, 3 December: 2.6 µg/m³, 0.3× usualMagnaMagna, 26 November: 4.8 µg/m³, 0.7× usualMagna, 27 November: 15.0 µg/m³, 2.1× usualMagna, 28 November: 24.1 µg/m³, 3.3× usualMagna, 29 November: 26.5 µg/m³, 3.7× usualMagna, 30 November: 20.4 µg/m³, 2.8× usualMagna, 1 December: 13.7 µg/m³, 1.9× usualMagna, 2 December: 0.9 µg/m³, 0.1× usualMagna, 3 December: 1.5 µg/m³, 0.2× usualSpanish ForkSpanish Fork, 26 November: 5.6 µg/m³, 1.1× usualSpanish Fork, 27 November: 8.9 µg/m³, 1.7× usualSpanish Fork, 28 November: 12.0 µg/m³, 2.3× usualSpanish Fork, 29 November: 18.8 µg/m³, 3.5× usualSpanish Fork, 30 November: 36.8 µg/m³, 6.9× usualSpanish Fork, 1 December: 21.1 µg/m³, 4.0× usualSpanish Fork, 2 December: 1.0 µg/m³, 0.2× usualSpanish Fork, 3 December: 2.5 µg/m³, 0.5× usualOremOrem, 26 November: 4.1 µg/m³, 0.6× usualOrem, 27 November: 13.7 µg/m³, 2.0× usualOrem, 28 November: 15.1 µg/m³, 2.2× usualOrem, 29 November: 19.7 µg/m³, 2.8× usualOrem, 30 November: 35.7 µg/m³, 5.1× usualOrem, 1 December: 19.9 µg/m³, 2.8× usualOrem, 2 December: 1.1 µg/m³, 0.2× usualOrem, 3 December: 1.6 µg/m³, 0.2× usualHighlandHighland, 26 November: 5.9 µg/m³, 1.2× usualHighland, 27 November: 7.4 µg/m³, 1.5× usualHighland, 28 November: 4.5 µg/m³, 0.9× usualHighland, 29 November: 7.2 µg/m³, 1.4× usualHighland, 30 November: 28.2 µg/m³, 5.6× usualHighland, 1 December: 20.2 µg/m³, 4.0× usualHighland, 2 December: no readingHighland, 3 December: no readingBountifulBountiful, 26 November: 5.8 µg/m³, 0.9× usualBountiful, 27 November: 11.4 µg/m³, 1.7× usualBountiful, 28 November: 17.5 µg/m³, 2.6× usualBountiful, 29 November: 24.1 µg/m³, 3.6× usualBountiful, 30 November: 25.8 µg/m³, 3.9× usualBountiful, 1 December: 16.1 µg/m³, 2.4× usualBountiful, 2 December: 0.8 µg/m³, 0.1× usualBountiful, 3 December: 0.5 µg/m³, 0.1× usual26 Nov272829301 Dec23
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.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
PocatelloIdaho, United States1 39.129 November4.87.8×
Spanish ForkUtah, United States1 36.830 November5.36.9×
HerrimanUtah, United States2 31.030 November3.76.2×
HighlandUtah, United States1 28.230 November4.15.6×
OremUtah, United States1 35.730 November7.05.1×
West JordanUtah, United States2 32.629 November7.64.3×
BountifulUtah, United States1 25.830 November6.73.9×
MillcreekUtah, United States2 34.629 November9.43.7×
MagnaUtah, United States1 26.529 November7.23.7×
Salt Lake CityUtah, United States2 28.330 November8.03.5×

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 31 of 41 episodes in the United States since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 41.

Use this page

SmogRank, Utah, United States, November 2023: 10 cities with PM2.5 at twice their usual or more, 29 to 30 November 2023, smogrank.com/episodes/2023-11-utah-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.