Winter 2020-2021 Summary – Warmer, Wetter and Snowier Than Average

South view of Great Blue Hill in winter.

Blue Hill Observatory
Winter 2020-2021 Summary:

The winter (December-February) season was generally warm with a few cold periods and with above average precipitation and snowfall. The 24-hour mean temperature for the winter of 30.5 deg F was 3.0 degrees warmer than the 130-year winter average and 1.5 degrees warmer than the 1981-2010 30-year average. The average maximum temperature was 37.2 deg F, which was just 0.4 deg F warmer than the 30-year winter mean, and the average minimum temperature of 24.2 deg F was 2.7 deg F warmer than the 30-year mean. Each month of the season was warmer than average, and the warmest days included a high temperature of 62F on December 1st, and 61F on December 25th, which was among the warmest Christmas Days on record. The coldest days during winter were the last three days of January, which included the season low temperature of 2F on January 31st. The liquid equivalent precipitation total for winter was 15.32 inches, which was nearly three inches more than the 130-year average and more than two inches above than the 1981-2010 mean. Winter snowfall totaled 65.9 inches, which was more than 21 inches greater than both the long-term mean and the 30-year average. There were several significant storms during winter, including a rain and snow storm on December 4th-6th, which brought 2.20 inches of precipitation and 2.8 inches of snow, a warm rain storm on December 25th, which brought 2.15 inches of rainfall, and a snow and rain storm on February 1st-2nd, which brought 14.3 inches of snow and 2.77 inches of liquid precipitation. Several other snowfalls in February left a total of 39.0 inches of snow during that month, making February the seventh snowiest on record. Following a recent trend, the local ponds, after initially freezing over in mid-December, froze and thawed several times during December and January, though they remained frozen during much of February. The mean wind speed for the winter months was only 12.2 mph, which was the lowest on record for any December-February period and more than 4 mph less than the long-term average. The peak gust during winter was 68 mph from the south-southeast on December 25th. Winter sunshine was below average with 352.5 hours, or 42 percent of the possible bright sunshine, which was six percent less than the long-term mean. 

BHO Lowest Winter (Dec-Feb) Mean Wind Speed, mph (1885-1886 to 2020-2021):

1) 12.2 in 2020-2021
2) 12.8 in 2019-2020
3) 13.1 in 2013-2014
   13.1 in 2018-2019
5) 13.3 in 2011-2012
   13.3 in 2014-2015
   13.3 in 2017-2018
8) 13.5 in 2015-2016

Mike Iacono
Chief Scientist
Blue Hill Observatory