Cold Weather on Boston’s Doorstop to Deliver Late First Frost

Boston has been a holdout in the transition to cooler temperatures. The city has missed its average first frost date, which usually arrives by Nov. 5. However, come Friday morning, Nov. 7, Bostonians could face freezing morning temperatures as overnight lows are expected to be at or below freezing in the city for the first time this fall.

The first frost of the season, also called the “first freeze,” is recorded as the date when overnight lows dip to freezing (32 degrees) or below. In New England, the first frost occurs within the first two weeks of October in the northern portions of New Hampshire, Vermont, and Maine. This fall, the first frost was fairly on time across the region.

The Boston Globe, however, notes that Boston will again have a later-than-average first frost date, marking five consecutive years in which freezing temperatures have been kept at bay thus far in November.

According to The Globe, warmer sea-surface temperatures along the New England coast have allowed surface air temperatures to remain somewhat elevated.

"Simply put, over the past 10 years, Boston has seen a later first frost date extend past the climatological (30-year) average eight times," noted The Globe's Ken Mahan. "The atmosphere is simply getting warmer due to climate change, and it's the same with the oceans. With both the air and seas warming, we just don't see colder air as early or as often."

Further analysis reveals that since 1970, the date of the first frost in Boston has shifted by a week, according to Climate Central. A warming climate also extends the growing season for insects and some pollen-producing plants.

Mahan observed that, upon looking at the same data set across the country, the contiguous United States has seen an increase of 2.4 degrees in the average temperature since 1970.