Cold Snap Forecast for Pennsylvania: The Next Arctic Blast
In Philadelphia the coldest week is usually Jan 21 to 27, with a normal low of 25°F, and the coldest night of the last 10 winters was 4°F on Jan 7, 2018.
Reading the National Weather Service forecast for Philadelphia.
Normals and records at Philadelphia International Airport
Coldest week
Jan 21 to 27Normal low 25°F
Coldest night, last 10 winters
4°FJan 7, 2018
First freeze
Nov 15Median of 10 winters
Record low
−7°FTwice, last on Jan 22, 1984 (records since 1940)
The coldest week in Pennsylvania, station by station
The week with the lowest normal low at each reference station, from NOAA’s 1991 to 2020 normals, beside the coldest night of the last 10 winters, the median first freeze and the record low.
The coldest week and the coldest nights at Pennsylvania reference stations
Station
Coldest week
Normal low
Coldest night, last 10 winters
First freeze
Record low
PhiladelphiaPhiladelphia International Airport, USW00013739
Jan 21 to 27
25°F
4°FJan 7, 2018
Nov 15
−7°FTwice, last on Jan 22, 1984records since 1940
PittsburghPittsburgh International Airport, USW00094823
Jan 20 to 26
21°F
−11°FJan 31, 2026
Oct 27
−22°FJan 19, 1994records since 1948
HarrisburgHarrisburg Capital City Airport, USW00014751
Jan 22 to 28
24°F
−4°FJan 31, 2019
Nov 7
−9°FTwice, last on Jan 21, 1985records since 1939
WilliamsportWilliamsport, USW00014778
Jan 22 to 28
19°F
−6°FJan 31, 2019
Oct 29
−20°FJan 21, 1994records since 1948
ErieErie International Airport, USW00014860
Jan 26 to Feb 1
20°F
−9°FJan 30, 2026
Nov 10
−18°FTwice, last on Feb 16, 2015records since 1926
Normals from NOAA NCEI; nightly lows from GHCN-Daily, the winters of 2016 to 2017 through 2025 to 2026.
The panel at the top of this page sets the next 7 nights at Philadelphia against the normal low for each date and adds the Climate Prediction Center outlook for the two weeks after. Enter a ZIP for your own town; it uses the nearest of the 5 Pennsylvania reference stations.
At Philadelphia it is usually Jan 21 to 27, with a normal low of 25°F. At the other reference stations: Pittsburgh Jan 20 to 26 (21°F), Harrisburg Jan 22 to 28 (24°F), Williamsport Jan 22 to 28 (19°F) and Erie Jan 26 to Feb 1 (20°F). These are NOAA's 1991 to 2020 daily normals.
The normal low at Philadelphia reaches 32°F around Dec 13. The first actual freeze came around Nov 15 in the median of the last 10 winters, weeks ahead of the normal, because one clear calm night can run far below the average.
The coldest night of the last 10 winters at Philadelphia was 4°F on Jan 7, 2018, and the coldest night of a typical winter there was 11°F. Elsewhere: Pittsburgh −11°F on Jan 31, 2026, Harrisburg −4°F on Jan 31, 2019 and Williamsport −6°F on Jan 31, 2019. The record at the Philadelphia station is −7°F, most recently on Jan 22, 1984, in daily records since 1940.
At Philadelphia a typical recent winter brings 71 nights at 32°F or colder and 10 at 20°F or colder, the median of the last 10 seasons.
Each night's forecast low is compared with the NOAA normal low for that date at the nearest reference station. A night 20 or more degrees below normal is an arctic blast, and so is a night below zero where the normal low is 10°F or warmer. A night 10 to 19 below is a cold snap. A night 5 or more below, or a week that runs 3 or more below on average, is colder than normal, and a week 5 or more above is mild.
The normal lows and coldest weeks are NOAA's 1991 to 2020 daily climate normals for Philadelphia International Airport (USW00013739), Pittsburgh International Airport (USW00094823), Harrisburg Capital City Airport (USW00014751), Williamsport (USW00014778) and Erie International Airport (USW00014860). The recent winters, first dates and records come from the same stations' daily lows in NOAA's GHCN-Daily archive, the winters of 2016 to 2017 through 2025 to 2026. The 7 night forecast is the National Weather Service's and the outlook is the Climate Prediction Center's.
