Winter in Philly Shines: Snow, Cold and Surprising Forecast Fumbles

Philadelphia endured a winter that outshone expectations in both depth and duration. From early December through the end of February, average temperatures dropped below 33 °F—one of the lowest in over a century. The city received more than 20 inches of snow, landing it in the top 20 % of all recorded U.S. winters for snowfall.

Forecasts vs Reality

Despite these predictions, Philadelphia ended up with 30 inches of snow—a dramatic 150 % increase over the expected amount—and temperatures that trended colder than average throughout the season.

The Science Behind the Surprise

• High‑Pressure Block over Greenland
  A persistent high‑pressure system trapped cold air and storms in the eastern U.S., while the west remained relatively warm.

• Negative Arctic Oscillation
  The oscillation stayed in its negative phase for most of the winter, allowing cold air to spill farther south than usual.

• Sea Ice Loss Near Greenland
  Melting ice lets more solar energy warm the water, altering upper‑atmosphere pressure patterns and fostering unusually cold pockets.

Even though global temperatures are about 2 °F warmer than a century ago, these localized changes in sea ice and atmospheric pressure can produce extreme cold events.

Long‑Term Trends vs Short‑Term Reality

In the early 2000s, Philadelphia winters had generally been warmer than the long‑term average. This trend led forecasters to anticipate above‑normal temperatures for several consecutive years. The 2025–26 winter, however, defied that pattern with colder-than-average days, illustrating how long‑term trends can sometimes mislead short‑term predictions.

Takeaway

The winter of 2025–26 serves as a stark reminder that weather can still surprise us. Even when forecasts appear reliable, unusual atmospheric conditions—such as high‑pressure blocks and Arctic Oscillation shifts—can turn a mild season into one of the coldest and snowiest on record.