May 2016 Summary – Warmer and Drier Than Average

Blue Hill Observatory
May 2016 Summary:

The month was notable for starting cool and finishing warm with less precipitation than average, though it was cool, cloudy and wet during the first week. The 24-hour mean temperature for the month of 57.2 deg F was 1.9 degrees warmer than the 120-year average for May and about a degree warmer than the 1981-2010 30-year average. The highest temperature for the month was 92F on the 28th, which surpassed the previous record for the date of 90F in 1914. The low temperature for the month of 38F occurred on the 16th. May precipitation totaled 3.13 inches, which was about an inch less than the long-term 120-year average and about a half inch less than the 30-year mean. Measurable rainfall was recorded on each of the first eight days of the month, bringing about half of the monthly total, 1.60 inches, over this period. This was the first time on record that May began with eight consecutive days with measurable precipitation. A trace of frozen precipitation fell in the form of sleet on the 1st, which tied the daily record for frozen precipitation for the date. There was one thunderstorm day on the 24th as early morning thunderstorms moved through the area that day. The mean wind speed was 11.3 mph, which tied for the fourth slowest for May, with a prevailing direction from the west. The peak gust for the month was 50 mph from the west on the 15th. May sunshine got off to a very slow start with no sunshine observed during the first five days. This was the least amount of sunshine ever recorded in the first five days of May surpassing the previous low of 30 minutes on 1-5 May 2012. The monthly average sunshine was well below average with 47 percent of the possible bright sunshine being observed, which was 5 percent less than the long-term average.

BHO Slowest May Wind Speed, mph (1885-2016)

1) 10.0 in 2012
2) 11.2 in 1982
11.2 in 2003
4) 11.3 in 2013
   11.3 in 2016
6) 11.4 in 1999
11.4 in 2014

Spring (Mar-May) 2016 Summary:

The Spring season was warmer and drier than average. The 24-hour mean temperature for Spring (March-May) of 47.8 deg F was 3.0 degrees warmer than the 120-year average for Spring and nearly two degrees warmer than the 1981-2010 30-year average. This made the season the 9th warmest Spring on record and the warmest since 2012. Precipitation for Spring totaled 10.70 inches, which was about an inch and a half less than the 120-year mean and about three and a half inches less than the 30-year normal. Spring snowfall totaled 19.4 inches, with most of this falling during the first week of April. Spring sunshine was 52 percent of possible, which was two percent more than the long-term average.

BHO Warmest Spring (Mar-May), deg F (1885-2016)

1) 51.3 in 2010
2) 50.9 in 2012
3) 49.4 in 1991
4) 49.0 in 1977
5) 48.4 in 1998
6) 48.2 in 1976
7) 48.1 in 1945
8) 47.9 in 1903
9) 47.8 in 2016
10) 47.6 in 1973

Mike Iacono
Chief Scientist
Blue Hill Observatory