If you're not a "winter person", then the first three weeks of January 2021 were tolerable, as temperatures were six degrees above average (with every day but two above average), and there was no snow (average high/low was 43°/33°). Then, the jet stream shifted, and the last nine days of the month were five degrees colder than average (high/low of 33°/22°). On the last day of the month conditions became even more wintry. Up until the 31st, it appeared the month was going to be among the five least snowy Januarys on record, as just 0.1" had fallen. But then, the opening volley of snow from a snowstorm that would bury the City on Feb. 1 dropped two inches between 6:00 and midnight - the most snow to fall on this date since 1898.
Despite being 2.2 degrees above average, January's mildest reading was just 51° (on Jan. 2). This was, by far, the mildest January to have its warmest reading this cool. Previous Januarys with mildest readings that were either 50°, 51°, or 52°, had an average monthly temperature of 28.9°, which is is 5.9 degrees colder than January 2021 (34.8°).
The coldest day of the month was the 29th, with a high/low of 25°/14° (thirteen degrees colder than average). This was the coldest day in two years (since a high/low of 21°/11° on Feb. 1, 2019).
With just 2.1" measured, this was the third consecutive January with snowfall that was well below average (January 2019, had 1.1", January 2020 had 2.3"). It was the fifth string of low-snow Januarys.
With an average high of 39.7°, and an average low of 29.8°, January's diurnal variation was just 9.9 degrees, making this just the third January whose average high and low was less than ten degrees apart. The two others were in 2017 and 1869 (variations of 9.4 and 9.8 degrees, respectively). This narrow diurnal variation was largely due to the month's average low being notably more above average than the average high (+2.9 degrees vs. +1.4 degrees, respectively).
Here are previous January recaps: