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December 2020

Dry Months in New York

Drier than normal

 

For the purposes of this analysis a dry month is one that had less than two inches of precipitation.  In the years since 1869, 18% of all months have been this dry, or about two months each year.  The most dry months in one year is six, which happened in 1910, 1946 and 1965.  The most consecutive months with less than two inches measured is four, which occurred in 1881 from July thru October.  Finally, there have been 15 years in which no month had less than two inches - most recently in 2018 (two of these 15 years were consecutive, in 2010 and 2011).

 

Graph - precip of less than 2 inches by month

 

CONSECUTIVE DRY MONTHS WITHIN A YEAR

The most consecutive months with less than two inches of precipitation is four, which happened in 1881 between July-October (1.25", 0.86", 0.97" and 1.60").  There have been nine other years that had three dry months in a row, the most recent being in 1993.  The smallest amount of rain during one of these streaks was 2.98" in 1910 (July-Sept.).

 

Chart - 3 months in a row with less than 2 inches

 

Two of the three years that have had six months with less than two inches of precipitation, 1910 and 1965, are among New York's ten driest years, but the third, 1946, is ranked 27th.

Five Octobers in a row from 1946-1950 had less than two inches of rain.  And there have been three other months that had this little precipitation in four consecutive years: January 1954-57; May 1902-05 and September 1884-87.  And seven of the nine Novembers between 1901-09 had two inches or less.

 

LESS THAN ONE INCH OF RAIN

Nearly one out of four dry months had less than one inch of rain, or about once every two years.  The greatest number of these very dry months in one year is three and it's happened twice, in 1881 and 1955.  The most years in a row to have the same month report less than one inch is two, which has happened three times: July 1954 (0.96") & 1955 (0.51"); Sept. 1884 (0.21") & 1885 (0.41"); and Oct. 2000 (0.68") & 2001 (0.66").

 

DRIEST MONTH OF EACH YEAR

On average, the driest month of a year has had 1.24" of precipitation (and most likely to happen in October).  About 40% of all years have had less than an inch of precipitation during their driest month.  June 1949 is the driest month of all time, with just 0.02" measured; the driest month in recent years is October 2013, which had just 0.36". The most consecutive years with a driest month reporting less than an inch is four, which was between 1999-2002.  

Thirteen years have had more than two inches as their driest month.  And two of them had more than three inches: 3.04" in 1975 and 3.03" in 2011. 

In both 1980 and 1981 the driest month had 0.58" of precipitation, and it was in consecutive months - Dec. 1980 and Jan. 1981.  And later in 1981, August had 0.59".  Two other years' second-driest month also had just 0.01" more than the driest month (1900 and 1975), while 1926's second driest month had 0.02" more.  And in 2000, 2001 and 2002 the driest months had 0.68", 066" and 0.71", respectively.

In the three consecutive years between 1903-1905, May was the driest month, and in the three consecutive years 1945-1947, October was the driest month.  Finally, in the four-year period 1967-1970 three of the years had January as their driest month (1967, 1968 and 1970).

 

Graph - driest month of year since 1869

 

Arid


Notable December Cold Snaps

The weather outside is frightful

Nearly 40% of Decembers since 1869, or 59, have experienced cold snaps/cold waves that lasted five days or longer (about half were seven+ days).  The most recent occurred in 2017.  In addition to the five-days+ qualifier, a cold snap needed to have an average high temperature of 32° or colder to be part of this analysis.  The longest of them lasted 15 days, in 1876; six have had sub-zero readings; six had twelve inches of of snow or more; and six had no snow whatsoever (not even a trace).  Finally, six Decembers had two periods of Arctic cold.

 

COLDEST

The coldest December cold wave occurred in 1917, when the six days between Dec. 17-22 had an average high/low of 17°/2°.  Most recently, the last six days of Dec. 2017 had an average high/low of 23°/15°, which tied for ninth coldest.

 

Chart - coldest december cold snaps

LENGTHIEST

Fifteen Decembers have had cold waves lasting ten or more days.  The lengthiest was 16 days in Dec. 1904 (average high of 32°/22°), followed by a 15-day stretch in 1876 (27°/17°).  The coldest of these lengthy cold waves was one of 10 days in 1872 (24°/10°).

 

Chart - lengthiest december cold waves

 

TWO IN ONE MONTH!

Six Decembers had two significant cold snaps.  The last time it happened was in 1955, with one of five days and the other lasting six days (they were three days apart).  The two in 1917 covered 15 days (eight days apart).

 

Chart - decembers with two cold snaps

 

COLD SNAPS MORE PREVALENT 100+ YEARS AGO

The greatest concentration of Decembers with cold waves was between 1876 and 1904, when 20 of the 29 Decembers had at least one cold snap.  The most consecutive Decembers to have a cold snap is four, which has happened four times: in 1901-1904, 1914-1917, 1932-35 and 1942-45; there have also been four three-year streaks, with the most recent being 1958-1960.  The most consecutive years without a cold snap is eight, and it's happened twice, in 1981-1988 and 2001-2008.  And there was a seven-year hiatus from 2010 to 2016.

 

SNOWIEST & LEAST SNOWY

Six cold snaps received more than 13 inches of snow.  The most was 22.5" in 1883 and 21.5" in 1872.  The most recent was in 2000 when 13.3" fell.  Five of the Decembers had snowstorms that dumped a foot or more, with the most being 18.0" on Dec. 26, 1872.  And although December 1942, with 6.0", isn't found on the "most snowy" list below, it's worth mentioning because it had measurable snow on six of the cold wave's ten days.

 

Chart - snowiest december cold snaps

 

At the other end of the snow spectrum, ten December cold snaps had no measurable snow.  Eight of them were five or six days in duration, but December 1870 and December 1989 lasted 11 and 10 days, respectively.

 Chart - december cold snaps with no snow

BELOW ZERO READINGS

Seven of the Decembers had at least one sub-zero low.  The most recent was in 1980 (on Christmas Day).  These cold waves accounted for all of the twelve sub-zero lows that have been reported in December.  And although December 1872 had no below-zero readings, it had the distinction of having six days in a row with lows in the single digits (ranging from 4° to 8°).  At the other end of the spectrum, the coldest temperatures of five December cold snaps was a relatively mild 18° or 19° (most recently in 1970).

 

Chart - subzero readings in december

 

 

Frigid-cold-blast-to-strike-usa


The Coldest Day of New York Winters

Frozen bryant park fountain

 

Since 1900 the average high/low on the coldest day of each winter has been 19°/6° (in the last third of the 18th century it was 14°/2°; in the 21st century it's risen to a relatively temperate 20°/9°).  The coldest day has occurred as early as Nov. 30 (winter of 1875-76) and as late as March 15 (winter of 1931-32).  Nearly half of the coldest days of New York's winters have occurred in the four-week period between Jan. 9 and Feb. 6.  For this analysis "coldest day" is based on daily mean temperature (average of high/low), not just the low temperature.

 

Chart - warming of coldest winter day

 

THE SPECTRUM OF THE BIG CHILL

The dates of the most frigid coldest winter day and the mildest coldest winter day are, in their respective years, one day apart.  The coldest of them all fell on Dec. 30, 1917, when the high/low was 2°/-13°.  At the other end of the spectrum, the mildest reading to have the distinction of being the coldest day of a winter was 31°/20° in the winter of 2001-02 on Dec. 31, 2001January 18 is the date to see the most coldest days of winter - six.  Three dates in February have been the coldest for five winters each: Feb. 2, Feb. 5 and Feb. 17.

 

Chart - coldest day jan 18
 

TWO MEASURES OF "COLDEST"

Although the coldest day is usually the same date as the coldest temperature, they have occasionally occurred on different dates (on average, in one out of four winters).  For instance, although the coldest reading of all time is -15°, the coldest day of all time, based on mean temperature, had a low of -13°.  Although this is two degrees "warmer" than the coldest reading, the day's high of 2° was six degrees colder than the high on Feb. 9, 1934, so it ended up with a mean of -5.5° compared to a -3.5° in 1934.  (The most recent instance was the winter of 2019-20 as its coldest day was on Dec. 19, with a high/low of 25°/16°, while the coldest reading was 14° on 2/15.)

 

SIMILAR DATES

A number of consecutive years, or a few years apart, have had their coldest day on practically the same date.  And in one interesting case the coldest day of winters one hundred years apart (1916 and 2016) occurred on the same date - Feb. 15.  And the coldest day of the winters of 1884 and 1984 were two days apart, on 12/23 and 12/25, respectively.

 

Chart - coldest day same date

Chart - coldest day same date - 2

Chart - coldest day same date 100 years apart 

FRIGID HOLIDAYS

The coldest day of some winters has fallen on a holiday.  The one exception is Christmas Eve day.

 

Chart - coldest winter day on holidays

 

"COLDEST COLDEST, MEET MILDEST COLDEST!"

Of course, the coldest winters have a lot of very cold days that that would easily qualify as the coldest dates of many of the winters with average or above average temperatures.

 

Chart - coldest coldest day of winter 
 Chart - mildest coldest day of winter

 

SOMETIMES IT SNOWS

Snow falls very infrequently on the coldest day of the winter - just six winters have had an inch or more of snow on this day.  However, a few were significant, with the stand out being the 12.5" accumulation on the coldest day of the winter of 1966-67 (Feb. 9, which had a high/low of 16°/7°).

 

Chart - snowy coldest days of winter

Finally, the coldest day of the winter of 1963-64 was preceded by a snowstorm that dumped 11.5" the day before, while three storms that followed the coldest day of winter by one day dumped more than ten inches.  The storm in February in 2003 dumped 16.3", but started on the coldest day of the winter, with 3.5" falling that evening.

 

Chart - snowy day before and after coldest day

   

 

Frigid

 

 

 

 

 


November 2020 Reigns As Mildest November On Record

WashSqPk_Nov2020

 

November 2020 was 5.2 degrees warmer than average and became the warmest November on record, supplanting November 2015 by 0.2 degrees.  Sixteen days had highs in the 60s or 70s (one fewer than the 1931 record).  What stood out was a streak of six days with highs in the 70s from Nov. 6-11, the longest such streak to occur in November.  (And the seven days between Nov. 4-10 all had clear or mostly sunny skies.) Conditions on Thanksgiving Day were noteworthy as well.  Although the high of 65° wasn't the warmest on record (it tied for third warmest), its low of 55° was.  (Just two years ago Thanksgiving Day had a high/low of 28°/17°.)  It was also one the seventh rainiest Thanksgiving, with 0.79" falling in the morning.  What follows are a few other observations:

 

  • Typically, November is 5.4 degrees cooler than April.  This year, however, it was 2.4 degrees milder and became just the tenth November to be milder than April.  (Nov. 1975 was warmer than April by the greatest margin, +4.4 degrees.)
  • The eight-day period between Nov. 5-12 was 14 degrees above average.  The rest of the month was two degrees above average.  These 22 days included four days that were ten or more degrees above average and two other days that were ten or more below average.  Overall the month had nineteen days that were five or more degrees above average.
  • At 3.99", the month's rainfall was an average amount, and that was thanks to a rainstorm that brought 0.98" on the last day of the month.  It was also the month's biggest rainstorm.  This storm was accompanied by gusty winds.  The peak gust was 35 mph, which was the seventh day of the month to report a peak gust of 30 mph or greater (the area's three major airports, LGA, JFK and EWR had gusts of 30 mph+ on ten, twelve and nine days, respectively, and their peak gusts were much higher).

 

Chart - wind gusts nov 2020 

  • The three warmest Novembers have all occurred in the 21st century, as well as half of the ten warmest and half of the top 12.
  • Despite being the warmest November on record, this November is tied with Nov. 2011 for warmest average high and tied for fourth mildest average low.  Additionally, Nov. 2020 had two days with sub-freezing low temperatures (both were 30°) while half of the ten mildest Novembers had coldest readings that were above freezing.
  • Besides this November, Nov. 1994 and Nov. 1975 also had six days in the 70s (but they weren't consecutive).  But they rank second behind Nov. 1953, which had seven such days.

 
 Chart - 10 mildest novembers2

Here are five previous November recaps:

2019

2018

2017

2016

2015

 

 Nov 7 high rises on hudson