Cool air will plunge out of Eastern Canada into New England Thursday night into Friday. A departing cold front will open the doors to the fall-like airmass that will settle in on Friday. By Friday morning, the temperature in interior Southern New England will be in the 40s, with low to mid 50s at the immediate coast and in the cities. It will be even cooler in Northern New England where the temperature will dip into the upper 30s to low 40s near dawn.
Overall, this looks like the coolest airmass to hit New England since early to mid June. The temperature at TF Green Airport has not been below 53° since June 6, 2013. It has not been that cool in Boston since May 28, 2013. The fall preview will not be long-lived, with highs in the 70s expected this weekend.