For meteorologists and climatologists—who need consistent dates to compare weather statistics year over year—winter is defined by the calendar months.
Runs from December 1 to February 28 (or 29th in leap years). The Two Definitions of Winter when is winter in united states
| Region | Winter Period | Average Temperature | | --- | --- | --- | | Northeast | Dec 21 - Mar 31 | 25°F - 40°F | | Midwest | Dec 21 - Mar 31 | 15°F - 30°F | | South | Dec 21 - Feb 28 | 40°F - 60°F | | West Coast | Dec 21 - Feb 28 | 40°F - 60°F | | Alaska | Sep 22 - Mar 20 | -20°F - 20°F | when is winter in united states