2016 Was the Second Warmest Year on Record

The year 2016 ended with a 24-hour corrected mean temperature of 51.2F, which was 3.6F warmer than the 120-year mean and 2.3F above the 30-year normal. This was the second warmest year on record behind only the mean of 51.7F observed in 2012. The annual average maximum temperature of 60.6F was the second highest on record behind only 60.8F in 2012, and the annual average minimum temperature of 42.8F was the fifth warmest on record. The year got off to a very warm start, and the trend continued all year as each month was warmer than the 120-year long-term average. Winter 2015-2016 (December-February) was the warmest on record, Spring 2016 (March-May) was the 9th warmest, August and the combined summer months (June-August) were the warmest on record and Fall 2016 was the 7th warmest relative to the 120-year mean. The maximum temperature for the year was 96F on July 22nd and 25th. These were two of the eleven 90-degree days in July, which was the second most in any July behind only the 14 observed in 1952. Seven consecutive days in July reached 90F or higher from the 22nd to the 28th, and this was the third longest heat wave in the Observatory’s history for any month and the longest in July. There were 17 90-degree days during the year, which was eleven more than the long-term average. The coldest temperature during 2016 was -14F on February 14th, which surpassed the previous record low temperature for the date of -8F in 1979. This reading was also the coldest temperature measured at the Observatory since -16F on January 15th, 1957 and the coldest in February since -16F on February 16th, 1943. This extreme low temperature on February 14th was followed by a rapid increase in temperature to a high of 55F two and a half days later. This rise of 69 degrees in roughly 60 hours tied the largest temperature increase on Blue Hill in less than 72 hours since records began in 1885. The other swing of 69 degrees in that time occurred from December 30th, 1933 to January 1st, 1934 when the temperature climbed from -18F to 51F.

A residual effect of the warmth in late 2015 was the very late freezes last winter of two local ponds, which occurred on January 6th, 2016. Both ponds remained frozen for only 50 days, and both Houghton’s Pond and Ponkapoag Pond were considered free of ice on February 25th, about three weeks earlier than the average date. The first ripe blueberries were observed on the summit of Great Blue Hill on June 7th, which is about two weeks earlier than the average date. Late in the year, the continued warmth delayed the freeze of both Houghton’s and Ponkapoag until December 19th, 2016.

Annual precipitation totaled 39.80 inches, which was about nine inches drier than the 120-year average and more than thirteen inches less than the 1981-2010 30-year average. This was the driest year since 1995. Only three months during 2016 exceeded the long-term average precipitation: February, April and October. The remaining months were all drier than average, with July being the driest month with only 1.50 inches, and the summer (June-August) was the third driest on record with only 4.90 inches of rain falling all summer. October brought the most liquid equivalent precipitation of any month with 7.04 inches. There were 15 days with thunderstorms during the year, which was seven fewer than average. A thunderstorm on February 25th was accompanied by a high temperature of 62F, heavy rain, and the highest wind gust of the year to 76 mph from the south. A thunderstorm on December 29th occurred during a burst of 1.8 inches of snow that followed a steady rain that day. The heaviest rainfall event of the year occurred on October 9th, when the greatest rainfall in 24 hours, 1.89 inches, was observed during the passage of the remnants of former Hurricane Matthew.

Snowfall for the calendar year was near average with a total of 64.0 inches, or three inches more than the long-term annual average of 61 inches. About a third of this snowfall, 22.5 inches, fell in February. The largest single snowfall during the winter months of 12.5 inches occurred on February 5th, and this storm was followed by another 8.7 inches on February 8th. A significant early Spring snowfall of 15.0 inches, the largest of the year, occurred on April 3rd-4th.  This was followed by bitterly cold temperatures for early April that bottomed out at 19F on April 5th, and included a new daily record low maximum temperature of 28F on April 4th, breaking the previous record for the date of 32F set in 1896, 1908 and 1975. The final snowfall for the 2015-2016 season was 57.5 inches, which was a few inches less than the long-term average seasonal snowfall.

The mean station pressure on the summit of Great Blue Hill during 2016 was 29.30 inches, which was 0.01 inches higher than the long-term annual mean of 29.29 inches. The highest sea-level pressure during the year was 30.78 inches on December 26th, which was the highest reading since 30.88 inches on November 25th, 2015. The lowest sea-level pressure during 2016 of 29.13 inches occurred on February 25th during a spring-like rain storm that included thunder, temperatures in the 60s, and strong winds.

The annual mean wind speed of 12.3 mph tied for the fourth lowest on record with 2014, behind only the 11.8 mph mean observed in 2012 and 12.2 mph recorded in 2013 and 2015. This continues the several decade long trend of decreasing mean wind speeds on Blue Hill. The peak wind gust for the year was 76 mph from the S during a thunderstorm and warm temperatures on February 25th.

Bright sunshine for the year was very high at 57 percent of possible, which was five percent more than the long-term average, and the total for 2016 was the most bright sunshine for any year since 2001.

BHO Warmest Annual 24-hour Mean Temperature, deg F (1885-2016):

1) 51.7 in 2012
2) 51.2 in 2016
3) 51.0 in 2010
4) 50.9 in 1999
5) 50.8 in 1998
6) 50.6 in 2006
7) 50.5 in 1953
8) 50.4 in 2011
9) 50.3 in 1990
   50.3 in 1991

BHO Warmest Annual Average Maximum Temperature, deg F (1885-2016):

1) 60.8 in 2012
2) 60.6 in 2016
3) 60.5 in 1949
4) 60.2 in 1999
5) 60.1 in 1953
   60.1 in 2010

BHO Warmest Annual Average Minimum Temperature, deg F (1885-2016):

1) 44.0 in 2012
2) 43.2 in 1998
3) 43.1 in 2006
4) 43.0 in 2010
5) 42.8 in 2016

BHO Lowest Annual Mean Wind Speed, mph (1885-2016):

1) 11.8 in 2012
2) 12.2 in 2013
   12.2 in 2015
4) 12.3 in 2014
   12.3 in 2016
6) 12.5 in 2011
7) 12.6 in 2008
   12.6 in 2009

BHO Highest Annual Total Sunshine, hours (1886-2016):

1) 2583.4 in 1965 [60%] 2) 2554.2 in 1963 [59%] 3) 2527.1 in 1966 [59%] 4) 2520.2 in 1964 [58%] 5) 2497.1 in 1978 [58%] 6) 2494.1 in 2001 [58%] 7) 2493.8 in 1976 [58%] 8) 2476.3 in 1899 [58%] 9) 2475.7 in 1908 [57%] 10) 2468.6 in 2016 [57%]

Mike Iacono
Chief Scientist
Blue Hill Observatory