Summer 2018, from a meteorological perspective, is now in the books. June, July and August proved to be a very warm and humid period across the Northeast and New England, with many sites recording a top 5 warmest summer…topped off by a record warm August. Numerous locations recorded their highest number of summer days with low temperatures greater than 70F and a record number of hours with dew points at or above 70F.Here on the Cape, our hottest day of the summer actually came very near the end of August. On the 29th, readings climbed into the 90s at all 4 “official” weather observing locations…Falmouth, Hyannis, Chatham and Provincetown…and heat index values (feels like temperatures) pushed 100F at times as dew point values held in the middle and upper 70s.
At Hyannis, where temperatures peaked at 91F on the 29th, the month finished nearly 5F above the long-term average! Total rainfall was below normal at Hyannis (2.80″ vs 3.63″) and at many other locations. However, a couple of rounds of thunder and heavy downpours earlier in the month did allow parts of the Lower and Outer Cape to exceed their normal August rainfall.
Flipping the calendar to September means we have stepped into meteorological Autumn – the months of September, October and November.
September is often a very nice weather month on the Cape as temperatures remain mild but the humidity starts to ease. Daytime highs are generally in the 70s and nighttime lows are in the 50s and 60s. That said, readings can easily climb into the 80s as they have over the last couple of days and it’s not impossible for the Cape to touch 90F despite the shortening days, lowering sun angle and cooling seas surface temperatures.
The average high on September 1st at Hyannis is 75.6F…and the average high by month’s end is down to a “cool” 67.2F.
What is perhaps most notable is the change in daylight that occurs through the month. On September 1st, sunrise at Hyannis is at 6:07AM and sunset is at 7:14PM…yielding a total of 13 hours 7 minutes and 12 seconds of daylight. On September 30th the sunrise is at 6:36AM and sunset is at 6:24PM, giving us just 11 hours 47 minutes and 29 seconds of daylight.