SmogRank / Episodes / Norway

Southern Norway, 4 January 2025

For 1 day, on 4 January 2025, 10 cities in Norway had PM2.5 at least twice their usual for the time of year. The worst reading was Fredrikstad, Østfold, Norway: 56.4 µg/m³ on 4 January, about 6.3× its usual 9.0. Ended 4 January.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached10in 1 country
Days14 January 2025
Worst day4 January10 cities counted
Furthest above usual6.3×Fredrikstad

Day by day

4 January 10 cities at twice their usual or more
GjøvikLillehammerGothenburgKristiansandBrumunddalDrammenPorsgrunnMossOsloStrømmenLillestrømSarpsborgElverumFredrikstad
1 Jan234567
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

FredrikstadFredrikstad, 1 January: 3.0 µg/m³Fredrikstad, 2 January: 11.7 µg/m³Fredrikstad, 3 January: 13.4 µg/m³Fredrikstad, 4 January: 56.4 µg/m³, 6.3× its usual 9.0Fredrikstad, 5 January: 21.8 µg/m³Fredrikstad, 6 January: 4.5 µg/m³Fredrikstad, 7 January: 3.2 µg/m³ElverumElverum, 1 January: 2.9 µg/m³Elverum, 2 January: 27.8 µg/m³Elverum, 3 January: 31.3 µg/m³Elverum, 4 January: 51.1 µg/m³, 5.9× its usual 8.6Elverum, 5 January: 23.1 µg/m³Elverum, 6 January: 2.5 µg/m³Elverum, 7 January: 1.0 µg/m³SarpsborgSarpsborg, 1 January: 4.0 µg/m³Sarpsborg, 2 January: 23.1 µg/m³Sarpsborg, 3 January: 16.3 µg/m³Sarpsborg, 4 January: 43.8 µg/m³, 4.3× its usual 10.2Sarpsborg, 5 January: 21.7 µg/m³Sarpsborg, 6 January: 4.0 µg/m³Sarpsborg, 7 January: 4.6 µg/m³LillestrømLillestrøm, 1 January: 6.6 µg/m³Lillestrøm, 2 January: 22.2 µg/m³Lillestrøm, 3 January: 16.6 µg/m³Lillestrøm, 4 January: 41.9 µg/m³, 3.8× its usual 10.9Lillestrøm, 5 January: 26.3 µg/m³Lillestrøm, 6 January: 6.8 µg/m³Lillestrøm, 7 January: 2.2 µg/m³StrømmenStrømmen, 1 January: 6.6 µg/m³Strømmen, 2 January: 22.2 µg/m³Strømmen, 3 January: 16.6 µg/m³Strømmen, 4 January: 41.9 µg/m³, 3.7× its usual 11.3Strømmen, 5 January: 26.3 µg/m³Strømmen, 6 January: 6.8 µg/m³Strømmen, 7 January: 2.2 µg/m³PorsgrunnPorsgrunn, 1 January: 7.1 µg/m³Porsgrunn, 2 January: 11.7 µg/m³Porsgrunn, 3 January: 15.2 µg/m³Porsgrunn, 4 January: 33.2 µg/m³, 2.6× its usual 12.9Porsgrunn, 5 January: 16.7 µg/m³Porsgrunn, 6 January: 16.5 µg/m³Porsgrunn, 7 January: 15.6 µg/m³DrammenDrammen, 1 January: 6.1 µg/m³Drammen, 2 January: 9.6 µg/m³Drammen, 3 January: 15.0 µg/m³Drammen, 4 January: 31.4 µg/m³, 2.5× its usual 12.4Drammen, 5 January: 15.8 µg/m³Drammen, 6 January: 4.3 µg/m³Drammen, 7 January: 1.6 µg/m³OsloOslo, 1 January: 3.8 µg/m³Oslo, 2 January: 13.5 µg/m³Oslo, 3 January: 12.7 µg/m³Oslo, 4 January: 28.6 µg/m³, 3.6× its usual 8.0Oslo, 5 January: 19.8 µg/m³Oslo, 6 January: 3.9 µg/m³Oslo, 7 January: 2.2 µg/m³MossMoss, 1 January: 4.5 µg/m³Moss, 2 January: 3.2 µg/m³Moss, 3 January: 12.0 µg/m³Moss, 4 January: 27.2 µg/m³, 3.5× its usual 7.7Moss, 5 January: 18.3 µg/m³Moss, 6 January: 4.7 µg/m³Moss, 7 January: 2.0 µg/m³BrumunddalBrumunddal, 1 January: 12.4 µg/m³Brumunddal, 2 January: 16.1 µg/m³Brumunddal, 3 January: 8.3 µg/m³Brumunddal, 4 January: 26.0 µg/m³, 2.1× its usual 12.4Brumunddal, 5 January: 23.1 µg/m³Brumunddal, 6 January: 10.6 µg/m³Brumunddal, 7 January: 2.7 µg/m³1 Jan234567
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
FredrikstadØstfold, Norway1 56.44 January9.06.3×
ElverumInnlandet, Norway1 51.14 January8.65.9×
SarpsborgØstfold, Norway1 43.84 January10.24.3×
LillestrømAkershus, Norway1 41.94 January10.93.8×
StrømmenAkershus, Norway1 41.94 January11.33.7×
OsloOslo, Norway1 28.64 January8.03.6×
MossØstfold, Norway1 27.24 January7.73.5×
PorsgrunnTelemark, Norway1 33.24 January12.92.6×
DrammenBuskerud, Norway1 31.44 January12.42.5×
BrumunddalInnlandet, Norway1 26.04 January12.42.1×

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 Norway

Number 2 of 5 episodes in Norway since our records began, by cities reached.

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

Use this page

SmogRank, Southern Norway, 4 January 2025: 10 cities with PM2.5 at twice their usual or more, 4 January 2025, smogrank.com/episodes/2025-01-04-southern-norway (accessed 5 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.