SmogRank / Episodes / United States
North-western United States and Canada, October and November 2023
For 3 days, from 31 October to 2 November 2023, 15 cities in the United States and Canada had PM2.5 at least twice their usual for the time of year. The worst reading was Salem, Oregon, United States: 38.3 µg/m³ on 1 November, about 5.6× its usual 6.9.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 15 in 2 countries
Days 3 31 October to 2 November 2023
Worst day 1 November 11 cities counted
Furthest above usual 5.6× Salem
Day by day
Play 1 November 11 cities at twice their usual or more
Tri-Cities Pasco Pendleton Walla Walla Moses Lake Ellensburg The Dalles Wenatchee Redmond Pullman Bend Moscow Gresham Issaquah Orchards Auburn Salmon Creek Milwaukie Vancouver Renton Portland Bellevue Canby Tacoma Columbia City Tigard Beaverton Seattle Shoreline Longview Marysville Hillsboro Lacey Centralia Bremerton Forest Grove Penticton McMinnville Mount Vernon Meridian Corvallis Oak Harbor Eugene Boise Kelowna Anacortes Chilliwack Bellingham Abbotsford Aberdeen Port Angeles Langley Victoria Roseburg Strawberry Hill Port Coquitlam Coquitlam Langford Delta Burnaby Ashland Medford Richmond Vancouver North Vancouver West Vancouver Duncan Grants Pass North Cowichan Squamish Coos Bay Harewood Nanaimo Missoula Twin Falls Port Alberni Courtenay Campbell River Yakima Spokane Altamont Lewiston Sunnyside Spokane Valley Albany Nampa Cranbrook Woodburn Dallas Hermiston Parkland Coeur d'Alene Salem 28 Oct 29 30 31 1 Nov 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
Salem Salem, 28 October: 8.3 µg/m³ Salem, 29 October: 11.2 µg/m³ Salem, 30 October: 16.3 µg/m³ Salem, 31 October: 34.0 µg/m³, 5.0× its usual 6.8 Salem, 1 November: 38.3 µg/m³, 5.6× its usual 6.9 Salem, 2 November: 7.6 µg/m³ Salem, 3 November: 18.1 µg/m³ Salem, 4 November: 4.8 µg/m³ Salem, 5 November: 4.2 µg/m³ Albany Albany, 28 October: 7.2 µg/m³ Albany, 29 October: 12.3 µg/m³ Albany, 30 October: 20.0 µg/m³ Albany, 31 October: 30.8 µg/m³, 4.2× its usual 7.4 Albany, 1 November: 22.9 µg/m³ Albany, 2 November: 7.9 µg/m³ Albany, 3 November: 13.4 µg/m³ Albany, 4 November: 3.9 µg/m³ Albany, 5 November: 4.4 µg/m³ Woodburn Woodburn, 28 October: 6.4 µg/m³ Woodburn, 29 October: 10.3 µg/m³ Woodburn, 30 October: 12.2 µg/m³ Woodburn, 31 October: 30.6 µg/m³, 4.7× its usual 6.5 Woodburn, 1 November: 28.9 µg/m³, 4.3× its usual 6.7 Woodburn, 2 November: 7.4 µg/m³ Woodburn, 3 November: 12.4 µg/m³ Woodburn, 4 November: 4.2 µg/m³ Woodburn, 5 November: 4.1 µg/m³ Parkland Parkland, 28 October: 12.5 µg/m³ Parkland, 29 October: 22.0 µg/m³ Parkland, 30 October: 22.2 µg/m³ Parkland, 31 October: 28.3 µg/m³, 5.2× its usual 5.4 Parkland, 1 November: 24.7 µg/m³ Parkland, 2 November: 4.1 µg/m³ Parkland, 3 November: 6.0 µg/m³ Parkland, 4 November: no reading Parkland, 5 November: no reading Dallas Dallas, 28 October: 6.9 µg/m³ Dallas, 29 October: 7.0 µg/m³ Dallas, 30 October: 20.2 µg/m³ Dallas, 31 October: 25.7 µg/m³, 5.1× its usual 4.5 Dallas, 1 November: 22.8 µg/m³ Dallas, 2 November: 4.9 µg/m³ Dallas, 3 November: 12.3 µg/m³ Dallas, 4 November: 5.0 µg/m³ Dallas, 5 November: 3.8 µg/m³ Lewiston Lewiston, 28 October: 17.2 µg/m³ Lewiston, 29 October: 16.5 µg/m³ Lewiston, 30 October: 14.7 µg/m³ Lewiston, 31 October: 22.8 µg/m³ Lewiston, 1 November: 32.7 µg/m³, 3.8× its usual 8.6 Lewiston, 2 November: 11.2 µg/m³ Lewiston, 3 November: 12.1 µg/m³ Lewiston, 4 November: 10.1 µg/m³ Lewiston, 5 November: 9.8 µg/m³ Altamont Altamont, 28 October: 10.0 µg/m³ Altamont, 29 October: 17.8 µg/m³ Altamont, 30 October: 18.8 µg/m³ Altamont, 31 October: 16.5 µg/m³ Altamont, 1 November: 31.5 µg/m³, 3.8× its usual 8.2 Altamont, 2 November: 35.9 µg/m³ Altamont, 3 November: 17.6 µg/m³ Altamont, 4 November: 10.4 µg/m³ Altamont, 5 November: 5.0 µg/m³ Cranbrook Cranbrook, 28 October: 25.6 µg/m³ Cranbrook, 29 October: 27.3 µg/m³ Cranbrook, 30 October: 24.9 µg/m³ Cranbrook, 31 October: 29.2 µg/m³ Cranbrook, 1 November: 29.4 µg/m³, 4.0× its usual 7.4 Cranbrook, 2 November: 34.4 µg/m³, 4.6× its usual 7.4 Cranbrook, 3 November: 13.0 µg/m³ Cranbrook, 4 November: 17.1 µg/m³ Cranbrook, 5 November: 8.2 µg/m³ Coeur d'Alene Coeur d'Alene, 28 October: 21.0 µg/m³ Coeur d'Alene, 29 October: 20.3 µg/m³ Coeur d'Alene, 30 October: 17.7 µg/m³ Coeur d'Alene, 31 October: 18.8 µg/m³ Coeur d'Alene, 1 November: 28.9 µg/m³, 4.1× its usual 7.0 Coeur d'Alene, 2 November: 37.7 µg/m³, 5.4× its usual 7.0 Coeur d'Alene, 3 November: 14.5 µg/m³ Coeur d'Alene, 4 November: no reading Coeur d'Alene, 5 November: no reading Yakima Yakima, 28 October: 10.9 µg/m³ Yakima, 29 October: 16.1 µg/m³ Yakima, 30 October: 19.2 µg/m³ Yakima, 31 October: 21.1 µg/m³ Yakima, 1 November: 28.8 µg/m³, 3.2× its usual 9.0 Yakima, 2 November: 32.4 µg/m³, 3.6× its usual 9.1 Yakima, 3 November: 20.6 µg/m³ Yakima, 4 November: 12.9 µg/m³ Yakima, 5 November: 9.6 µg/m³ Hermiston Hermiston, 28 October: 11.3 µg/m³ Hermiston, 29 October: 13.8 µg/m³ Hermiston, 30 October: 17.7 µg/m³ Hermiston, 31 October: 20.7 µg/m³ Hermiston, 1 November: 27.6 µg/m³, 5.1× its usual 5.4 Hermiston, 2 November: 27.6 µg/m³, 5.1× its usual 5.4 Hermiston, 3 November: 9.4 µg/m³ Hermiston, 4 November: 15.4 µg/m³ Hermiston, 5 November: 2.8 µg/m³ Spokane Spokane, 28 October: 19.0 µg/m³ Spokane, 29 October: 23.5 µg/m³ Spokane, 30 October: 22.3 µg/m³ Spokane, 31 October: 20.6 µg/m³ Spokane, 1 November: 26.2 µg/m³, 3.8× its usual 6.9 Spokane, 2 November: 24.8 µg/m³ Spokane, 3 November: 12.9 µg/m³ Spokane, 4 November: 11.1 µg/m³ Spokane, 5 November: 5.0 µg/m³ Sunnyside Sunnyside, 28 October: 10.3 µg/m³ Sunnyside, 29 October: 17.6 µg/m³ Sunnyside, 30 October: 20.1 µg/m³ Sunnyside, 31 October: 18.7 µg/m³ Sunnyside, 1 November: 25.5 µg/m³, 3.4× its usual 7.4 Sunnyside, 2 November: 29.3 µg/m³, 4.0× its usual 7.4 Sunnyside, 3 November: 18.2 µg/m³ Sunnyside, 4 November: 15.4 µg/m³ Sunnyside, 5 November: 7.1 µg/m³ Spokane Valley Spokane Valley, 28 October: 20.7 µg/m³ Spokane Valley, 29 October: 22.0 µg/m³ Spokane Valley, 30 October: 18.8 µg/m³ Spokane Valley, 31 October: 20.6 µg/m³ Spokane Valley, 1 November: 25.0 µg/m³, 3.7× its usual 6.7 Spokane Valley, 2 November: 29.6 µg/m³, 4.2× its usual 7.0 Spokane Valley, 3 November: 10.8 µg/m³ Spokane Valley, 4 November: 10.8 µg/m³ Spokane Valley, 5 November: 5.3 µg/m³ Nampa Nampa, 28 October: 9.7 µg/m³ Nampa, 29 October: 10.7 µg/m³ Nampa, 30 October: 11.9 µg/m³ Nampa, 31 October: 11.8 µg/m³ Nampa, 1 November: 21.8 µg/m³ Nampa, 2 November: 28.1 µg/m³, 4.3× its usual 6.6 Nampa, 3 November: 23.6 µg/m³ Nampa, 4 November: no reading Nampa, 5 November: no reading 28 Oct 29 30 31 1 Nov 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
Salem Oregon, United States 2 1 November 6.9 5.6× Coeur d'Alene Idaho, United States 2 2 November 7.0 5.4× Parkland Washington, United States 1 31 October 5.4 5.2× Hermiston Oregon, United States 2 1 November 5.4 5.1× Dallas Oregon, United States 1 31 October 4.5 5.1× Woodburn Oregon, United States 2 31 October 6.5 4.7× Cranbrook British Columbia, Canada 2 2 November 7.4 4.6× Nampa Idaho, United States 1 2 November 6.6 4.3× Albany Oregon, United States 1 31 October 7.4 4.2× Spokane Valley Washington, United States 2 2 November 7.0 4.2× Sunnyside Washington, United States 2 2 November 7.4 4.0× Lewiston Idaho, United States 1 1 November 8.6 3.8× Altamont Oregon, United States 1 1 November 8.2 3.8× Spokane Washington, United States 1 1 November 6.9 3.8× Yakima Washington, United States 2 2 November 9.1 3.6×
Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.
Against other episodes in the United States and Canada
Number 74 of 141 episodes in the United States and Canada since our records began, by cities reached.
Eastern United States and Canada, 25 June to 2 July 2023 280 North-eastern United States and Canada, July 2026 264 Eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, 30 July to 9 August 2025 241 Eastern United States and Canada, July 2023 240 North-eastern United States and Canada, 3 to 9 June 2025 196 Eastern United States and Canada, 14 to 19 June 2023 161 North-eastern United States and Canada, 12 to 16 July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, 10 to 14 June 2025 104 North-western United States and Canada, 4 to 11 August 2026 99 North-eastern United States and Canada, 14 to 19 February 2026 96 North-western United States and Canada, October and November 2023 15 Bars: cities reached; colour: the level of the episode's highest daily reading. All 141 .
Use this page SmogRank, North-western United States and Canada, October and November 2023: 15 cities with PM2.5 at twice their usual or more, 31 October to 2 November 2023, smogrank.com/episodes/2023-10-north-western-united-states-and-canada (accessed 4 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.
