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Blue Hill Observatory
May 2019 Summary:
May was generally cooler and cloudier than average, with slightly more rainfall than expected. The 24-hour adjusted mean temperature for the month of 54.4 deg F was 1.8 degrees cooler than the 120-year average for May and 0.9 degrees cooler than the 1981-2010 30-year average. The average maximum temperature of 63.5 deg F was nearly three degrees below normal, and the average minimum temperature of 46.0 deg F was nearly two degrees below normal. The highest temperature for the month was 85F on the 26th (the only day warmer than 80F), and the lowest temperature was 36F on the 12th. Precipitation totaled 4.61 inches, which was nearly an inch more than the long-term 120-year average and about a half inch more than the 30-year mean. The greatest amount in 24 hours was 1.24 inches on the 13th-14th. Despite the modest total rainfall, there were 21 days with measurable precipitation, which tied for the most ever in May and tied for the second most in any month of the year. There was one thunderstorm day during the month on the 26th. A trace of sleet was observed on the 12th, which was among the latest occurrences of frozen precipitation on record. The mean wind speed was 11.1 mph, and the prevailing direction was from the south. A peak gust of 47 mph from the northwest occurred on the 24th. May was the eleventh cloudiest on record with only 172.7 hours of bright sunshine, or 40 percent of possible, which was 12 percent less than the long-term average.
BHO Greatest May Number of Days Measurable Precipitation (1886-2019):
1) 21 in 1888
21 in 2019
3) 20 in 2005
4) 19 in 1943
5) 18 in 1924
18 in 2003
BHO Greatest Monthly Number of Days Measurable Precipitation (1886-2019):
1) 22 in December 1972
2) 21 in May 1888
21 in May 2019
3) 20 in July 1906
20 in April 1912
20 in October 1913
20 in June 1916
20 in April 1929
20 in January 1950
20 in May 2005
20 in April 2019
Spring (Mar-May) 2019 Summary:
Despite some warm days in April, Spring 2019 was generally cooler, wetter and cloudier than average. The 24-hour adjusted mean temperature for the Spring season of 45.5 deg F was 0.7 degrees warmer than the 120-year average, but it was 0.6 degrees cooler than the 1981-2010 30-year average. Precipitation during Spring totaled 16.83 inches, with about half of this amount occurring in April, and this total was about four and a half inches more than the 120-year average and about two and a half inches more than the 30-year normal. There were 51 days with measurable precipitation during Spring, which tied for the second most on record and was the most since 1929. Spring snowfall of 23.1 inches, which was all recorded during March, was about eight inches more than average. This included the largest snowfall from a single storm for the entire 2018-2019 winter season, which was 15.8 inches on March 3rd-4th. That storm was also the 10th largest snowstorm ever recorded during March at the Observatory. Spring was generally cloudier than average, especially April and May, with only 44 percent of the possible bright sunshine, which was six percent less than the long-term Spring average of 50 percent.
BHO Greatest Spring (Mar-May) Number of Days Measurable Precipitation (1886-2019):
1) 52 in 1912
2) 51 in 1916
51 in 1929
51 in 2019
5) 50 in 1908
50 in 1983
Mike Iacono
Chief Scientist
Blue Hill Observatory
