November is the month of the year with the greatest decline of the average temperature. The average high drops from 46 degrees on Nov. 1 to 27 degrees by Nov. 30. The average low plummets from 27 degrees to 11 degrees. This rapid decline is largely due to the development of snow cover which, often enough, begins during November.
Snow cover makes the weather colder by reflecting sunlight. However, if November remains dry and snow-free, like it did in 1999, temperatures can remain mild, with weather in the 50s and 60s even around Thanksgiving.
On the other hand, if deep snow comes early, as it did in 1985, the November weather can be like January.
In 1985, two feet of snow led to subzero temperatures on each of the last 11 days of the month, four of which were in the -20s. It should be noted that a snow-free early part of the winter does not guarantee a mild winter. Last winter did not turn particularly severe until after the middle of January.