April 2015 Summary – Warmer and Drier Than Average – Blue Hill Observatory & Science Center

Blue Hill Observatory April 2015 Summary: The month was notable for being generally warmer and drier than average with only a trace of frozen precipitation. The 24-hour mean temperature for the month of 46.7 deg F was 2.0 degrees warmer than the 120-year average for April, and it was about a half degree warmer than the 1981-2010 30-year average. The maximum temperature for the month was 69F on the 13th, and the coldest temperature was 26F on the 1st. This was only the twelfth year since 1885 in which the temperature did not reach 70 deg F by the end of April. The last time this occurred was in 1975. The average minimum temperature for January through April tied for the sixth coldest on record. April was drier than average with a precipitation total of 3.33 inches, which was about an inch less than the 120-year average and the 1981-2010 mean. The monthly snowfall of a trace, which fell as sleet on the 8th, was 2.9 inches less than the long-term average. This kept the seasonal total at 150.8 inches, which is a new seasonal snowfall record. The snow depth on the summit of Great Blue Hill dropped quickly from a high of 8 inches on the 1st to only a trace by the 4th. A residual effect of the cold weather in February and March was the very late thaws of two local ponds. Houghton’s Pond was considered free of ice on April 10th, which tied for the second latest thaw date ever observed, and Ponkapoag Pond was considered thawed on April 11th, which was the latest thaw date on record for that pond in the last 130 years. In a sign of spring, there were two thunderstorm days during the month on the 4th and the 21st, The mean wind speed for the month was 13.0 mph, which was the sixth slowest on record, and the prevailing direction was from the northwest. The peak gust for the month was 54 mph from the northwest on the 4th. April sunshine totaled 199.1 hours, or 51 percent of the possible bright sunshine, which was two percent more than the long-term average. BHO Lowest Jan-Apr Maximum Temperature, deg F (1885-2015) 1) 66 in 1924 2) 67 in 1893 67 in 1916 67 in 1939 67 in 1966 6) 68 in 1904 68 in 1975 8) 69 in 1917 69 in 1919 69 in 1937 69 in 1971 69 in 2015 BHO Coldest Jan-Apr Average Minimum Temperature, deg F (1885-2015) 1) 18.9 in 1885 2) 19.3 in 1888 3) 19.7 in 1923 4) 20.0 in 1904 5) 20.5 in 1934 6) 20.9 in 1893 20.9 in 1920 20.9 in 2015 9) 21.0 in 1887 10) 21.4 in 1907 Latest Houghton’s Pond Thaw Date, (1886-2015) 1) April 14, 1926 2) April 10, 1887 April 10, 1888 April 10, 2015 4) April 9, 1923 5) April 8, 1993 6) April 7, 1899 April 7, 1956 8) April 6, 1916 April 6, 1917 April 6, 1924 April 6, 1940 Latest Ponkapoag Pond Thaw Date, (1886-2015) 1) April 11, 2015 2) April 10, 1926 3) April 9, 1923 4) April 6, 1940 5) April 5, 1916 April 5, 1924 7) April 4, 1967 April 4, 1994 9) April 3, 1904 April 3, 1920