Washington's warmest winter on record Winter is over and the results are in: The winter of 2011-12 was Washington's warmest on record. The average temperature for astronomical winter - the period from December's winter solstice to Tuesday's spring equinox - was 45.6 degrees, according to the local National Weather Service forecast office. That was nearly two degrees above the previous record, set in 1989-90, the Weather Service said. Meteorologists treat the months of December, January and February as winter based on prevailing weather patterns. But the season is widely defined by the position of the sun as it appears in the sky, and it runs from solstice to equinox. In addition to its many warm days, this past winter was distinguished by the lack of truly cold ones. The temperature - as measured at Reagan National Airport - dipped to 32 degrees or below on only 24 of the season's 89 days. That was the fewest on record for Washington.