Cool air mass arrives to close out September

Despite the arrival of cooler air, Friday’s average temperature of 65 degrees was 6 degrees above normal. The last time a sub-normal temperature was recorded was September 11th. High temperatures on Saturday are expected to be limited to the mid 60s due to east winds, and the influence of a large area of high pressure over the Great lakes. Should this verify, it will be the coolest daytime reading in over 4 months. September, 2017 is likely to close as the 13th warmest September on record. This is remarkable, considering the first 12 days of the month averaged 4.4 degrees below normal. Since then, an unprecedented late-season heat wave helped amass a cumulative temperature surplus of 208 degrees, with the period averaging 13 degrees above normal.