BETHLEHEM, Pa. — It’s the kind of cold that exposes weak car batteries, drafty windows, questionable insulation and every decision you ever made involving thin gloves.
December temperatures in the Lehigh Valley have plunged far enough below normal to make even seasoned winter residents take notice.
It’s shaping up as one of the coldest starts to winter on record, with every single day of December 2025 colder than average thus far.
In fact, it was our coldest Dec. 1-15 period since 2005.
The last day with above-normal temperatures in the Allentown area was Nov. 26.
During the stretch, a record coldest high temperature of 25 degrees was set Friday, Dec. 5, breaking the previous daily record of 27 degrees set in 2002.
Temperature records for the area date to 1922.
Cold by the numbers
Climate perspectives data from the Northeast Regional Climate Center shows that from Dec. 1 through mid-month, the area’s average temperature ran 9.7 degrees below normal.
Five of those 15 days featured a daytime high at or below 32 degrees, while all 15 days saw a low (or minimum) temperature below the freezing mark.
Overnight lows failed to make it out of the teens Dec. 12-15. The repetitive pattern featured nights where lows were 16, 14, 16 and 14 degrees.
According to preliminary data from the National Weather Service, the wind chill was zero at 10:40 p.m. on Sunday, Dec. 14. At the time, the air temperature was 16 degrees, with winds out of the northwest at 17 mph.
It came following a winter storm that dumped up to 8 inches of snow in parts of the area.
Together, the departures make this stretch the fifth-coldest of the early-December periods in the station’s long-term record, which dates back more than a century.
Through mid-December, the city’s mean monthly temperature hovered near 27 degrees, a level more commonly associated with deep winter rather than the early holiday season.
A December that feels out of place
The sustained chill has given the Lehigh Valley a climate profile that looks less like eastern Pennsylvania and more like regions known for harsh winters.
Temperature patterns this month have closely resembled those seen in parts of the northern Plains and northern Rockies, where December cold is both expected and prolonged.
Unlike a brief Arctic blast that retreats after a few days, the pattern has lingered, keeping daytime temperatures suppressed and preventing meaningful warm-ups between cold snaps.
The Valley also is not alone. The cold gripping the area is part of a nationwide outbreak of Arctic air that has dominated weather headlines across much of the country.
Large portions of the Midwest, Great Lakes, Plains and Northeast have experienced repeated intrusions of bitter cold, driven by a southward dip in the polar vortex and a highly amplified jet stream.
In several regions, temperatures have plunged 20 to 30 degrees below average, with daily record lows challenged or broken.
Meteorologists note that the breadth and persistence of the cold have been notable, especially for early December.
When will it end?
Forecasts suggest that below-normal temperatures will continue Tuesday, under mostly sunny to partly cloudy skies.
But there finally are signs of a warmup ahead, with temperatures rising near 50 by Thursday and beneficial rain expected on Friday.
“Even with mild temperatures and a snowpack in place, ensemble river forecasts show less than a 10% chance of streams/rivers getting to action stage with the rain + ensuing snowmelt,” the weather service said in its latest forecast discussion.
Models suggest probabilities of 1 inch of rain or more hover around 40-60% for most of the region, the weather service said, noting the possibility of a “rain/snow mix on the backside of the precipitation shield,” but no significant snow accumulation is anticipated.
Even so, climatologists caution that December 2025 already has secured its place as one of the colder starts to winter in recent memory.
