SmogRank / Episodes / United States

North-western United States and Canada, September 2025

For 3 days, from 26 to 28 September 2025, 9 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Wenatchee, Washington, United States: 95.2 µg/m³ on 28 September, about 19× its usual 5.1.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached9in 2 countries
Days326 to 28 September 2025
Worst day27 September7 cities counted
Furthest above usual19×Wenatchee

Day by day

27 September 7 cities at twice their usual or more
PullmanWalla WallaTri-CitiesVernonHermistonSunnysideEllensburgYakimaChilliwackMarysvilleBothellKirklandBellevueInglewood-Finn HillRentonMissoulaPicnic Point-North LynnwoodAuburnColumbia CityMount VernonAbbotsfordShorelineSeattleBurienMissionBellinghamTacomaParklandAnacortesOak HarborBremertonLangleyPort CoquitlamCoquitlamLaceyStrawberry HillBurnabyDeltaCentraliaNorth VancouverVancouverRichmondSalmon CreekWest VancouverLongviewVictoriaSquamishPort AngelesLethbridgeLangfordNorth CowichanDuncanAberdeenButteNanaimoHarewoodHelenaLewistonKelownaMoscowSpokaneMoses LakeSpokane ValleyCoeur d'AleneCranbrookWenatchee
23 Sep242526272829301 Oct
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

WenatcheeWenatchee, 23 September: 48.8 µg/m³, 9.6× usualWenatchee, 24 September: 154.0 µg/m³, 30× usualWenatchee, 25 September: 46.1 µg/m³, 9.0× usualWenatchee, 26 September: 73.0 µg/m³, 14× usualWenatchee, 27 September: 26.5 µg/m³, 5.2× usualWenatchee, 28 September: 95.2 µg/m³, 19× usualWenatchee, 29 September: 80.3 µg/m³, 16× usualWenatchee, 30 September: 13.4 µg/m³, 2.6× usualWenatchee, 1 October: 15.0 µg/m³, 2.9× usualMoses LakeMoses Lake, 23 September: 10.0 µg/m³, 2.0× usualMoses Lake, 24 September: 17.4 µg/m³, 3.5× usualMoses Lake, 25 September: 41.2 µg/m³, 8.2× usualMoses Lake, 26 September: 34.5 µg/m³, 6.9× usualMoses Lake, 27 September: 18.4 µg/m³, 3.7× usualMoses Lake, 28 September: 29.8 µg/m³, 6.0× usualMoses Lake, 29 September: 26.2 µg/m³, 5.2× usualMoses Lake, 30 September: 4.9 µg/m³, 1.0× usualMoses Lake, 1 October: 3.1 µg/m³, 0.6× usualLewistonLewiston, 23 September: 15.9 µg/m³, 2.2× usualLewiston, 24 September: 10.2 µg/m³, 1.4× usualLewiston, 25 September: 9.9 µg/m³, 1.4× usualLewiston, 26 September: 34.0 µg/m³, 4.8× usualLewiston, 27 September: 30.3 µg/m³, 4.3× usualLewiston, 28 September: 17.0 µg/m³, 2.4× usualLewiston, 29 September: 15.2 µg/m³, 2.1× usualLewiston, 30 September: 6.2 µg/m³, 0.9× usualLewiston, 1 October: 4.2 µg/m³, 0.6× usualMoscowMoscow, 23 September: 11.7 µg/m³, 2.0× usualMoscow, 24 September: 8.2 µg/m³, 1.4× usualMoscow, 25 September: 12.5 µg/m³, 2.2× usualMoscow, 26 September: 29.9 µg/m³, 5.2× usualMoscow, 27 September: 23.5 µg/m³, 4.1× usualMoscow, 28 September: 15.3 µg/m³, 2.6× usualMoscow, 29 September: 12.0 µg/m³, 2.1× usualMoscow, 30 September: 6.1 µg/m³, 1.1× usualMoscow, 1 October: 4.9 µg/m³, 0.8× usualCranbrookCranbrook, 23 September: 5.2 µg/m³, 1.0× usualCranbrook, 24 September: 7.7 µg/m³, 1.4× usualCranbrook, 25 September: 16.9 µg/m³, 3.1× usualCranbrook, 26 September: 3.7 µg/m³, 0.7× usualCranbrook, 27 September: 42.9 µg/m³, 7.9× usualCranbrook, 28 September: 51.0 µg/m³, 9.4× usualCranbrook, 29 September: 15.3 µg/m³, 2.8× usualCranbrook, 30 September: 8.5 µg/m³, 1.6× usualCranbrook, 1 October: 2.2 µg/m³, 0.4× usualCoeur d'AleneCoeur d'Alene, 23 September: 11.6 µg/m³, 2.3× usualCoeur d'Alene, 24 September: 10.2 µg/m³, 2.0× usualCoeur d'Alene, 25 September: 22.1 µg/m³, 4.4× usualCoeur d'Alene, 26 September: 16.6 µg/m³, 3.3× usualCoeur d'Alene, 27 September: 41.1 µg/m³, 8.2× usualCoeur d'Alene, 28 September: 37.0 µg/m³, 7.4× usualCoeur d'Alene, 29 September: 15.0 µg/m³, 3.0× usualCoeur d'Alene, 30 September: 5.7 µg/m³, 1.1× usualCoeur d'Alene, 1 October: 3.0 µg/m³, 0.6× usualSpokane ValleySpokane Valley, 23 September: 8.0 µg/m³, 1.6× usualSpokane Valley, 24 September: 9.3 µg/m³, 1.9× usualSpokane Valley, 25 September: 21.0 µg/m³, 4.2× usualSpokane Valley, 26 September: 15.1 µg/m³, 3.0× usualSpokane Valley, 27 September: 35.3 µg/m³, 7.1× usualSpokane Valley, 28 September: 32.7 µg/m³, 6.5× usualSpokane Valley, 29 September: 15.4 µg/m³, 3.1× usualSpokane Valley, 30 September: 4.9 µg/m³, 1.0× usualSpokane Valley, 1 October: 2.5 µg/m³, 0.5× usualSpokaneSpokane, 23 September: 7.7 µg/m³, 1.5× usualSpokane, 24 September: 8.8 µg/m³, 1.7× usualSpokane, 25 September: 20.5 µg/m³, 4.0× usualSpokane, 26 September: 14.0 µg/m³, 2.7× usualSpokane, 27 September: 34.4 µg/m³, 6.7× usualSpokane, 28 September: 33.2 µg/m³, 6.5× usualSpokane, 29 September: 17.4 µg/m³, 3.4× usualSpokane, 30 September: 5.3 µg/m³, 1.0× usualSpokane, 1 October: 3.4 µg/m³, 0.7× usualKelownaKelowna, 23 September: 22.2 µg/m³, 4.4× usualKelowna, 24 September: 17.3 µg/m³, 3.4× usualKelowna, 25 September: 8.7 µg/m³, 1.7× usualKelowna, 26 September: 9.4 µg/m³, 1.8× usualKelowna, 27 September: 25.7 µg/m³, 5.0× usualKelowna, 28 September: 4.5 µg/m³, 0.9× usualKelowna, 29 September: 20.6 µg/m³, 4.0× usualKelowna, 30 September: 4.0 µg/m³, 0.8× usualKelowna, 1 October: 2.5 µg/m³, 0.5× usual23 Sep242526272829301 Oct
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
WenatcheeWashington, United States3 154.024 September5.130×
CranbrookBritish Columbia, Canada2 51.028 September5.49.4×
Moses LakeWashington, United States2 41.225 September4.98.2×
Coeur d'AleneIdaho, United States2 41.127 September4.98.2×
Spokane ValleyWashington, United States2 35.327 September4.57.1×
SpokaneWashington, United States2 34.427 September5.16.7×
MoscowIdaho, United States1 29.926 September5.85.2×
KelownaBritish Columbia, Canada1 25.727 September5.15.0×
LewistonIdaho, United States2 34.026 September7.14.8×

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 Canada

Number 81 of 106 episodes in the United States and Canada since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 106.

Use this page

SmogRank, North-western United States and Canada, September 2025: 9 cities with PM2.5 at twice their usual or more, 26 to 28 September 2025, smogrank.com/episodes/2025-09-north-western-united-states-and-canada-2 (accessed 2 October 2026).

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.