SmogRank / Episodes / United States

Pennsylvania, United States, February 2024

For 1 day, on 10 February 2024, 8 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Lancaster, Pennsylvania, United States: 43.6 µg/m³ on 10 February, about 4.7× its usual 9.2.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached8in 1 country
Days110 February 2024
Worst day10 February8 cities counted
Furthest above usual4.7×Lancaster

Day by day

10 February 8 cities at twice their usual or more
NorristownAllentownBethlehemChesterWilmingtonNewarkSewellBearEwingElktonTrentonSouth VinelandRandolphScrantonNew BrunswickDoverEdgewoodYorkLindenHunt ValleyPleasantvilleToms RiverAtlantic CityBaltimoreBayonnePatersonJersey CityNew York CityCarlisleFort LeeNew CityScaggsvilleSouth LaurelWhite PlainsNewburghRockvilleWashingtonRose HillSpringfieldHagerstownAshburnDanburyState CollegeBridgeportWaterburyNew HavenAltoonaAlbanyPittsfieldHartfordJohnstownSpringfieldNorth ChicopeeNew LondonCharlottesvilleGreenfieldHarrisonburgCoventryWorcesterMcKeesportWest MifflinWilkinsburgProvidencePittsburghPawtucketFall RiverLexingtonLowellBrocktonErieBostonQuincyHermitageWeirton HeightsWeirtonLynnSteubenvilleYoungstownWheelingWarrenPhiladelphiaHarrisburgPennsaukenLebanonBensalemReadingLancasterElizabeth
7 Feb8910111213
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

LancasterLancaster, 7 February: 14.0 µg/m³, 1.5× usualLancaster, 8 February: 20.1 µg/m³, 2.2× usualLancaster, 9 February: 12.9 µg/m³, 1.4× usualLancaster, 10 February: 43.6 µg/m³, 4.7× usualLancaster, 11 February: 25.2 µg/m³, 2.7× usualLancaster, 12 February: 19.6 µg/m³, 2.1× usualLancaster, 13 February: 6.4 µg/m³, 0.7× usualElizabethElizabeth, 7 February: 9.3 µg/m³, 1.3× usualElizabeth, 8 February: 19.7 µg/m³, 2.7× usualElizabeth, 9 February: 13.7 µg/m³, 1.9× usualElizabeth, 10 February: 35.0 µg/m³, 4.7× usualElizabeth, 11 February: no readingElizabeth, 12 February: no readingElizabeth, 13 February: 4.9 µg/m³, 0.7× usualBensalemBensalem, 7 February: 7.9 µg/m³, 0.9× usualBensalem, 8 February: 17.4 µg/m³, 1.9× usualBensalem, 9 February: 18.1 µg/m³, 2.0× usualBensalem, 10 February: 34.6 µg/m³, 3.8× usualBensalem, 11 February: 19.7 µg/m³, 2.2× usualBensalem, 12 February: 12.8 µg/m³, 1.4× usualBensalem, 13 February: 11.1 µg/m³, 1.2× usualLebanonLebanon, 7 February: 9.8 µg/m³, 1.2× usualLebanon, 8 February: 16.2 µg/m³, 1.9× usualLebanon, 9 February: 15.3 µg/m³, 1.8× usualLebanon, 10 February: 32.2 µg/m³, 3.8× usualLebanon, 11 February: 15.0 µg/m³, 1.8× usualLebanon, 12 February: 15.7 µg/m³, 1.8× usualLebanon, 13 February: 6.1 µg/m³, 0.7× usualHarrisburgHarrisburg, 7 February: 11.2 µg/m³, 1.3× usualHarrisburg, 8 February: 16.0 µg/m³, 1.8× usualHarrisburg, 9 February: 14.8 µg/m³, 1.7× usualHarrisburg, 10 February: 31.4 µg/m³, 3.5× usualHarrisburg, 11 February: 10.3 µg/m³, 1.2× usualHarrisburg, 12 February: 17.4 µg/m³, 2.0× usualHarrisburg, 13 February: 6.8 µg/m³, 0.8× usualReadingReading, 7 February: 8.2 µg/m³, 1.0× usualReading, 8 February: 13.4 µg/m³, 1.7× usualReading, 9 February: 14.1 µg/m³, 1.8× usualReading, 10 February: 30.9 µg/m³, 3.9× usualReading, 11 February: 13.9 µg/m³, 1.7× usualReading, 12 February: 11.8 µg/m³, 1.5× usualReading, 13 February: 5.4 µg/m³, 0.7× usualPennsaukenPennsauken, 7 February: 5.8 µg/m³, 0.7× usualPennsauken, 8 February: 12.1 µg/m³, 1.5× usualPennsauken, 9 February: 13.4 µg/m³, 1.6× usualPennsauken, 10 February: 29.7 µg/m³, 3.6× usualPennsauken, 11 February: 16.5 µg/m³, 2.0× usualPennsauken, 12 February: 10.2 µg/m³, 1.2× usualPennsauken, 13 February: 6.5 µg/m³, 0.8× usualPhiladelphiaPhiladelphia, 7 February: 6.9 µg/m³, 0.8× usualPhiladelphia, 8 February: 13.7 µg/m³, 1.6× usualPhiladelphia, 9 February: 13.6 µg/m³, 1.5× usualPhiladelphia, 10 February: 26.1 µg/m³, 3.0× usualPhiladelphia, 11 February: 16.5 µg/m³, 1.9× usualPhiladelphia, 12 February: 12.2 µg/m³, 1.4× usualPhiladelphia, 13 February: 7.1 µg/m³, 0.8× usual7 Feb8910111213
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
LancasterPennsylvania, United States1 43.610 February9.24.7×
ElizabethNew Jersey, United States1 35.010 February7.44.7×
ReadingPennsylvania, United States1 30.910 February8.03.9×
BensalemPennsylvania, United States1 34.610 February9.03.8×
LebanonPennsylvania, United States1 32.210 February8.53.8×
PennsaukenNew Jersey, United States1 29.710 February8.33.6×
HarrisburgPennsylvania, United States1 31.410 February8.93.5×
PhiladelphiaPennsylvania, United States1 26.110 February8.83.0×

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 126 of 131 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 131.

Use this page

SmogRank, Pennsylvania, United States, February 2024: 8 cities with PM2.5 at twice their usual or more, 10 February 2024, smogrank.com/episodes/2024-02-pennsylvania-united-states (accessed 3 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.