September 2013 Summary – Sunny and Dry

Blue Hill Observatory
September 2013 Summary:

The month was mostly dry with abundant sunshine, similar to August.  The 24-hour mean temperature for September of 61.9F was slightly warmer than the 120-year average, though it was slightly cooler than the recent 30-year normal for September.  The one 90-degree day during the month was also the maximum temperature of 93F on the 11th, which also tied the daily temperature record for the date set in 1983. This raises to 15 the total number of 90-degree days for 2013.  The coolest temperature was 40F on 17th and 24th. Although the total precipitation for September of 3.91 inches was only slightly less than average, most of this rainfall (2.75 inches) fell on the first two days of the month, which made the rest of the month seem very dry.  There were four thunderstorm days during September on the 1st, 2nd, 3rd and 12th, and this brings the total number of thunderstorm days for the year up to 22, which is close to the annual average.  The mean wind speed for September was only 10.6 mph, which is the lowest on record for the month, with a prevailing direction of W.  This surpasses the previous record of 10.7 mph in September 2011.  The peak wind gust for the month was only 38 mph from the S on the 22nd, and this was the lowest peak gust for September since 36 WNW was recorded in 2007.  Bright sunshine for the month was plentiful and totaled 65 percent, which was 9 points above the mean for September of 56 percent.