For weather and climate science, all of December is winter — no ambiguity. This matches most people’s experience of cold temperatures and snow in temperate Northern Hemisphere regions.
During the solstice, the North Pole is tilted at its furthest point away from the sun, resulting in the shortest day and longest night of the year. In this view, December is the "bridge" month where autumn takes its final bow. 2. The Meteorological Answer: Pure Winter is december winter or fall
Under the astronomical calendar, most of December (the 1st through the 20th or 21st) is still fall . Winter only starts around December 21. So, December 21–31 is winter, but December 1–20 is technically autumn. For weather and climate science, all of December
The official beginning of Winter .
Are you curious about how the specifically affects daylight hours in your region? In this view, December is the "bridge" month
In the Northern Hemisphere (which includes North America, Europe, and most of Asia), December is a winter month. Meteorological winter begins on December 1st, and the astronomical winter solstice (the official start of the season) occurs around December 21st or 22nd. While the very beginning of the month might technically still be considered late autumn by astronomical standards, culturally and weather-wise, December is firmly associated with winter.