A History of Biggest & Smallest Swings in Daily Temperatures in New York City

 

 

The range in daily temperature in Central Park, also known as diurnal variation, is typically 14 degrees, and ranges from 11 degrees in December and January, to 17 degrees in May.  However, variations by individual days generally range between five and thirty degrees.  Variations are affected by atmospheric conditions such as humidity, cloud cover, passage of cold/warm fronts, wind direction, and precipitation.

 

On Dec. 23, 2022 mild air drawn up the coast by a fast-moving coastal storm crashed into a strong Arctic front moving southeastward, resulting in a drop in temperature from 58° to 8°.  This 50-degree plunge established a new record for greatest temperature drop of any calendar date, breaking the previous record of a 48-degree nosedive more than 100 years earlier, on March 28, 1921.  (That drop, however, is more impressive because it happened in just 10 hours while 2022’s drop took twice as long.)

 

Drops in temperature of 40 degrees or more in a day are infrequent, with just 19 such instances reported since 1869 (about once every seven years).  However, this year’s was the first drop of 40+ degrees of the century; the previous occurrence was on Dec. 22, 1998.  (Oddly enough, 1962 and 1990 each experienced two of these drops.)

 

At the other end of the spectrum are daily variations of, one, two, or three degrees.  There have been only seven instances of days with a one-degree change (in other words, happening once every generation).  The last time was on Dec. 14, 1996 (the high/low was 40°/39°).  Days with variances of two degrees occur, on average, once every two years (most recently on May 13, 2018 when the high/low was 54°/52°).  And an average year sees one or two days with three-degree variations (most recently on Jan. 28, 2022 when the high/low was 32°/29°).

 

Most of the big daily swings in temperature have occurred between January and May. For the purposes of this analysis I chose changes of 33 degrees or more as the qualifier.  Swings of this magnitude have occurred nearly 200 times (thru 2022), an average of 1.3 days per year.  1990 has had the most - seven days.  (Sixteen years have had no such days, including three in a row from 1982 to 1984.)

 

By month, the smallest difference between the average high and low occurred in November 1977, when it was only 8.4 degrees (high of 51.5°/low of 43.1°).  The greatest difference between the high/low was 21.6 degrees in May 1941 (high of 75.5°/low of 53.9°).

 

Half of the months with variations less than 11 degrees have occurred since 2001, while just 20% of variations greater than 18 degrees have occurred in this century (the last time was in May 2015 when there was a 19.8 degree variation). This is likely a function of global warming, as overnight temperatures have risen at a faster rather than high temperatures.

 

Although daily temperature variations of two or three degrees occur just a couple of times each year, in 1970 there were five such occurrences in a fifteen-day period, between Dec. 11-25.

 

Finally, the most instances of a variation of 33+ degrees by date have occurred on April 19 and April 25, both which have had it happen six times.  April 25th's include the consecutive years of 1960, 1961 and 1962.

 

  

Comments

[Bobby Ruane]

This was fascinating reading.

[Harry]

You note the last time there was a 3 degree variation (November 13, 2020). When is the last time there was a 2 degree variation?

[Rob]

On May 13, 2018 (Mother's Day), the high/low was 54/52.

[Henry]

In the 1970-2020 period, April 4, 1995, had the warmest temperature (68 degrees) to plunge into a sub-freezing temperature (28 degrees) at the end of the day.