SmogRank / Episodes / United States
Pennsylvania, United States, December 2023
For 1 day, on 2 December 2023, 14 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Bensalem, Pennsylvania, United States: 36.5 µg/m³ on 2 December, about 4.2× its usual 8.6.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 14 in 1 country
Days 1 2 December 2023
Worst day 2 December 14 cities counted
Furthest above usual 5.3× Lexington
Day by day
Play 2 December 14 cities at twice their usual or more
New City Newburgh Paterson Fort Lee White Plains Jersey City New York City Elizabeth Bayonne Linden Danbury Bridgeport Waterbury Ewing New Haven Toms River Scranton Pittsfield Hartford Norristown Springfield North Chicopee Chester Pleasantville Atlantic City South Vineland Wilmington Greenfield Utica New London Bear Newark Elkton Dover Keene Coventry Worcester Syracuse Rutland Edgewood Providence Pawtucket Hunt Valley Fall River Baltimore Lowell Brockton Derry Boston Quincy Scaggsville Haverhill Lynn South Laurel Laconia Rockville State College Washington Portsmouth Rochester Hagerstown Ashburn Altoona Portland Johnstown Buffalo Kenmore St. Catharines Toronto York Lancaster Philadelphia Pennsauken Harrisburg Reading Bensalem Allentown Carlisle Lebanon Trenton Bethlehem Albany Lexington 29 Nov 30 1 Dec 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
Bensalem Bensalem, 29 November: 13.2 µg/m³, 1.5× usual Bensalem, 30 November: 17.7 µg/m³, 2.1× usual Bensalem, 1 December: 29.4 µg/m³, 3.4× usual Bensalem, 2 December: 36.5 µg/m³, 4.2× usual Bensalem, 3 December: 14.2 µg/m³, 1.7× usual Bensalem, 4 December: 9.8 µg/m³, 1.1× usual Bensalem, 5 December: 11.2 µg/m³, 1.3× usual Harrisburg Harrisburg, 29 November: 9.4 µg/m³, 1.3× usual Harrisburg, 30 November: 15.1 µg/m³, 2.0× usual Harrisburg, 1 December: 25.4 µg/m³, 3.4× usual Harrisburg, 2 December: 30.7 µg/m³, 4.1× usual Harrisburg, 3 December: 15.1 µg/m³, 2.0× usual Harrisburg, 4 December: 5.0 µg/m³, 0.7× usual Harrisburg, 5 December: 6.7 µg/m³, 0.9× usual Lebanon Lebanon, 29 November: 8.4 µg/m³, 1.1× usual Lebanon, 30 November: 12.2 µg/m³, 1.6× usual Lebanon, 1 December: 22.9 µg/m³, 3.0× usual Lebanon, 2 December: 33.6 µg/m³, 4.4× usual Lebanon, 3 December: 13.7 µg/m³, 1.8× usual Lebanon, 4 December: 5.0 µg/m³, 0.6× usual Lebanon, 5 December: 6.2 µg/m³, 0.8× usual Carlisle Carlisle, 29 November: 9.9 µg/m³, 1.4× usual Carlisle, 30 November: 14.4 µg/m³, 2.1× usual Carlisle, 1 December: 19.4 µg/m³, 2.8× usual Carlisle, 2 December: 30.0 µg/m³, 4.3× usual Carlisle, 3 December: 12.8 µg/m³, 1.9× usual Carlisle, 4 December: 4.1 µg/m³, 0.6× usual Carlisle, 5 December: 6.9 µg/m³, 1.0× usual York York, 29 November: 7.8 µg/m³, 0.9× usual York, 30 November: 9.5 µg/m³, 1.1× usual York, 1 December: 16.8 µg/m³, 1.9× usual York, 2 December: 30.0 µg/m³, 3.4× usual York, 3 December: 10.6 µg/m³, 1.2× usual York, 4 December: 6.0 µg/m³, 0.7× usual York, 5 December: 8.2 µg/m³, 0.9× usual Bethlehem Bethlehem, 29 November: 7.8 µg/m³, 1.2× usual Bethlehem, 30 November: 12.9 µg/m³, 2.0× usual Bethlehem, 1 December: 18.7 µg/m³, 2.9× usual Bethlehem, 2 December: 29.9 µg/m³, 4.7× usual Bethlehem, 3 December: 9.1 µg/m³, 1.4× usual Bethlehem, 4 December: 4.9 µg/m³, 0.8× usual Bethlehem, 5 December: 6.4 µg/m³, 1.0× usual Reading Reading, 29 November: 7.9 µg/m³, 1.1× usual Reading, 30 November: 11.5 µg/m³, 1.6× usual Reading, 1 December: 21.5 µg/m³, 3.0× usual Reading, 2 December: 29.8 µg/m³, 4.2× usual Reading, 3 December: 10.6 µg/m³, 1.5× usual Reading, 4 December: 5.4 µg/m³, 0.8× usual Reading, 5 December: 6.0 µg/m³, 0.8× usual Lancaster Lancaster, 29 November: no reading Lancaster, 30 November: 12.5 µg/m³, 1.6× usual Lancaster, 1 December: 21.3 µg/m³, 2.7× usual Lancaster, 2 December: 29.6 µg/m³, 3.7× usual Lancaster, 3 December: 10.7 µg/m³, 1.4× usual Lancaster, 4 December: 5.3 µg/m³, 0.7× usual Lancaster, 5 December: 7.0 µg/m³, 0.9× usual Philadelphia Philadelphia, 29 November: 8.8 µg/m³, 1.2× usual Philadelphia, 30 November: 12.7 µg/m³, 1.7× usual Philadelphia, 1 December: 19.0 µg/m³, 2.5× usual Philadelphia, 2 December: 28.7 µg/m³, 3.8× usual Philadelphia, 3 December: 11.4 µg/m³, 1.5× usual Philadelphia, 4 December: 6.8 µg/m³, 0.9× usual Philadelphia, 5 December: 7.6 µg/m³, 1.0× usual Albany Albany, 29 November: 4.5 µg/m³, 0.8× usual Albany, 30 November: 10.8 µg/m³, 1.9× usual Albany, 1 December: 12.6 µg/m³, 2.3× usual Albany, 2 December: 28.0 µg/m³, 5.0× usual Albany, 3 December: 6.4 µg/m³, 1.1× usual Albany, 4 December: 2.8 µg/m³, 0.5× usual Albany, 5 December: 5.6 µg/m³, 1.0× usual Trenton Trenton, 29 November: no reading Trenton, 30 November: 12.0 µg/m³, 2.0× usual Trenton, 1 December: 18.9 µg/m³, 3.1× usual Trenton, 2 December: 27.0 µg/m³, 4.4× usual Trenton, 3 December: 9.3 µg/m³, 1.5× usual Trenton, 4 December: 6.5 µg/m³, 1.1× usual Trenton, 5 December: 6.3 µg/m³, 1.0× usual Lexington Lexington, 29 November: no reading Lexington, 30 November: no reading Lexington, 1 December: 13.7 µg/m³, 2.7× usual Lexington, 2 December: 26.5 µg/m³, 5.3× usual Lexington, 3 December: no reading Lexington, 4 December: 3.7 µg/m³, 0.7× usual Lexington, 5 December: 5.6 µg/m³, 1.1× usual Allentown Allentown, 29 November: 7.7 µg/m³, 1.3× usual Allentown, 30 November: 11.1 µg/m³, 1.8× usual Allentown, 1 December: 18.9 µg/m³, 3.1× usual Allentown, 2 December: 25.6 µg/m³, 4.2× usual Allentown, 3 December: 9.6 µg/m³, 1.6× usual Allentown, 4 December: 4.9 µg/m³, 0.8× usual Allentown, 5 December: 5.5 µg/m³, 0.9× usual Pennsauken Pennsauken, 29 November: 6.4 µg/m³, 1.0× usual Pennsauken, 30 November: 9.9 µg/m³, 1.5× usual Pennsauken, 1 December: 17.1 µg/m³, 2.6× usual Pennsauken, 2 December: 25.0 µg/m³, 3.8× usual Pennsauken, 3 December: 8.1 µg/m³, 1.2× usual Pennsauken, 4 December: 5.1 µg/m³, 0.8× usual Pennsauken, 5 December: 6.2 µg/m³, 1.0× usual 29 Nov 30 1 Dec 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
Lexington Massachusetts, United States 1 2 December 4.2 5.3× Albany New York, United States 1 2 December 5.6 5.0× Bethlehem Pennsylvania, United States 1 2 December 6.4 4.7× Trenton New Jersey, United States 1 2 December 6.1 4.4× Lebanon Pennsylvania, United States 1 2 December 7.7 4.4× Carlisle Pennsylvania, United States 1 2 December 6.9 4.3× Bensalem Pennsylvania, United States 1 2 December 8.6 4.2× Reading Pennsylvania, United States 1 2 December 7.1 4.2× Allentown Pennsylvania, United States 1 2 December 6.1 4.2× Harrisburg Pennsylvania, United States 1 2 December 7.5 4.1× Pennsauken New Jersey, United States 1 2 December 6.5 3.8× Philadelphia Pennsylvania, United States 1 2 December 7.5 3.8× Lancaster Pennsylvania, United States 1 2 December 7.9 3.7× York Pennsylvania, United States 1 2 December 8.7 3.4×
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 26 of 41 episodes in the United States since our records began, by cities reached.
North-eastern United States and Canada, June and July 2023 279 North-eastern United States and Canada, May and June 2023 260 North-eastern United States and Canada, July 2023 241 North-eastern United States and Canada, June 2023 161 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, July 2023 75 Western United States, September 2023 61 South-eastern United States, October 2023 47 North-eastern United States, July 2023 46 North-western United States and Canada, May 2023 42 Western United States, December 2023 32 Northern United States, January 2023 32 Pennsylvania, United States, December 2023 14 Bars: cities reached; colour: the level of the episode's highest daily reading. All 41 .
Use this page SmogRank, Pennsylvania, United States, December 2023: 14 cities with PM2.5 at twice their usual or more, 2 December 2023, smogrank.com/episodes/2023-12-pennsylvania-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.
