March 2018 Weather Recap: Chronic Chill Follows Mildest February

 

 

 

For the second year in a row March was colder than February (both which were the mildest on record), a rarity that occurred just once before, in 1890 and 1891.  March 2018 will also be remembered for the four nor'easters that lashed the area in a three-week period as well as a 22-day streak with below-average temperatures.  This was the fifth March of the past six that was colder than average.  However, despite the chronic cold there were no Arctic outbreaks; the coldest low was just 27° (the coldest reading in March is typically in the upper teens) and the coldest high was 39° (the typical coldest high is around 32°).

 

FOUR NOR'EASTERS IN QUICK SUCCESSION

Nor'easter #1 (March 1-2) - This was a rain event, with 2.24" measured.  Colder air moved in as the storm exited in the early evening, briefly changing the rain to wet snow, but it didn't produce a measurable accumulation.

Nor'easter #2 (March 9) - This storm produced wet snow which accumulated 3.2" in the afternoon and evening.  Despite a prediction of 8-10" the accumulation was kept down because temperatures stayed above freezing.  Total liquid precipitation was 1.41".

Nor'easter #3 (March 13-14) - This was the least consequential of the storms.  Despite a prediction of significant snowfall there was no measurable accumulation, and just 0.36" of rain.  Curiously, Central Park was the only reporting site in the metro that didn't have measurable snow (JFK had 1.2" while LaGuardia and Newark both reported 0.3").

Nor'easter #4 (March 21-22) - This was the only storm of the four in which the temperature was 32° or colder for much of the duration.  As a result, a significant amount of snow, 8.4", piled up, making it one of the City's ten largest snowfalls after March 15. 

All but 0.11" of the month's 5.17" of precipitation came from these nor'easters.  This was the second month in a row with more than five inches of precipitation, the first time it happened since Dec. 2014/Jan. 2015.  The combined 11.00" that was measured was close to 50% above the average amount of precipitation for the two months (7.45").

 

MORE CHILLY THAN COLD

The 22-day streak with below average temperatures (March 7-28) was the fifth longest in the years since 1950.  But while it was one of the longest below-average streaks on record it wasn't a particularly cold one.  At 4.5 degrees below average it was the least below-average of any streak of 15 days or longer.  Another curious aspect about this March was that it shared some characteristics with Marches that were milder than average, i.e., very few lows in the 20s (just two), a coldest high that was around 40°, and no days that were ten degrees or more colder than average. 

Overall, March 2018 was 2.4 degrees colder than average, which was 1.8 degrees colder than February.  By comparison, March 2017 was 3.3 degrees below average and 2.4 degrees colder than February.  Typically, March is 6.2 degrees milder than February.

 

 

 

Other March recaps: 2017 and 2016

 

 

 

 

 

 

March 2017 Snaps 20-Month Streak of Above Average Temperatures

The mild conditions that made February 2017 the warmest on record continued at the onset of March as the high reached 70° on 3/1.  That would be the mildest reading of the month.  Through March 10 temperatures were three degrees above average, but then the next three weeks were six degrees below average, resulting in the entire month being 3.3 degrees colder than average - putting an end to New York's record streak of twenty months in a row with above average temperatures.  March was also colder than February, which, in the years since 1900, had happened only twice before (in 1984 and 1960).  And March's average low was colder than that of February, January or December.

 

 

ADDITIONAL HIGHLIGHTS

• True winter-like conditions were experienced during a six-day stretch from March 11-16, when temperatures were fifteen degrees below average and a snow and sleet storm snarled the City on 3/14.  7.6" accumulated, but most northern and western suburbs, which didn't have sleet, were buried by 15" to 24".  (If the 1.97" in liquid precipitation that was measured at Central Park had been all snow, about 20" would have piled up.)  The day after the storm the high was just 26°, which was 24 degrees below average.

 

 

• The month had five days with highs of 32° or colder, which was more than December (two), January (three) or February (one), as was the number of days with lows in the teens.  The low of 14° on 3/5 tied 1/10 as the coldest reading of the winter.

• After a a two-week period (March 10-23) that saw below average temperatures on all but one day (and averaging nine degrees below average), the rest of the month was mostly uneventful.

• The last week of the month received half of the month's 5.25" of precipitation, with all but one day reporting measurable rain.  This was the wettest March in six years.

• In a reverse of the time-worn saying, March came in like a lamb rather than a lion (70°), which is how it went out as an all-day rain brought 1.51" along with very chilly temperatures (high/low of 43°/37°).

 

 

• Finally, this was the fourth of the past five Marches to be significantly colder than average.  The March that wasn't colder than average, in 2016, was the fourth mildest on record.

 

 

 

 

 

Days With Desert-Like Humidty In The 21st Century

 

 

In April of 2016 New York experienced eleven days in a row with clear or sunny skies (4/12-22).  In addition to this abundance of blue skies, the streak was also characterized by extremely low humidity.  While typical late afternoon humidity levels in April are generally between 45% and 50%, during these eleven days it was mostly between 15% and 20%.  And at 5 PM on 4/20 it fell to 9%.  Since 2000, only one other day before 4/20/16 had a humidity level that was lower - March 31, 2007, which reported 6% humidity late in the afternoon (and on 4/6/21, the humidity dropped to 7%).  It was April 2016's streak of arid days was the inspiration for this post, which looks at hourly and monthly relative humidity reported in Central Park since 2000, with a focus on extremely low levels, which for the purposes of this analysis is 25% or lower.          

 

• Since 2000 5% of the days have had at least one hour with a relative humidity of 25% or lower (about 19 days/year).  The number of such days ranged from six in 2000 to 32 in 2010.  When I began this project I guessed that January and February might have the most days with the lowest humidity, but it turns out that two-thirds of the these days occurred in March or April.

 

 

• February, March and April have the lowest humidity, while September has the highest (followed closely by June).

• Not only were the two years with the lowest average humidity consecutive (2015, 2014), so were the years with highest average humidity (2003, 2004).  And while the year with lowest humidity had significantly lower than average precipitation, the second driest was well above average.  In fact, the total precipitation for the year with the highest humidity was very similar to this second driest year (58.56" vs. 57.79").

 

 

• During a typical day, the lowest and highest humidity levels occur about nine hours apart, with the highest occurring around daybreak (averaging 72%), and lowest levels during mid-afternoon, averaging in the mid-50s.

 

 

• There have been close to 50 days with at least one hour of humidity at 15% or lower (thru the end of April 2022).  All were in March or April, until 2018 when the humidity fell below 15% twice in May and once in November, and then again in Dec. 2021.  The lowest humidity to occur in the other months has been 16%, and it's happened on four dates: Feb. 26, 2014; May 3 and May 13 in 2007, and Sept. 11, 2001.

• The months with the least and most precipitation don't always have corresponding low and high average humidity.  For example, the most humid October and February had only 1.18" and 1.66" of precipitation, respectively.  The months with the least humidity don't have outliers quite that extreme, but the driest June and January had more than four inches of precipitation, which is close to average.

• In this century, months in the years 2000-2004 tended to have the highest average humidity while those with the lowest were clustered in the years since 2010.

 

 

 

  

 

   

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When April Isn't Much Warmer Than March

 

The month of April is typically 10.5 degrees milder than the month of March.  April 2020, however, was just 2.4 degrees milder, making its average temper the third closest to March of any April (going back to 1869).  The closest April came to March was in 1946 when April was 0.8 degrees milder than March.  The chart below lists the six Aprils that were closest to March's average temperature.

 

And although April 2020 wasn't chillier than March, it had no days in the 70s while March had three (making this the first April since 1940 not to have any readings of 70° or warmer).

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March 2016 - New York City's Fourth Mildest, Sixth Driest

 

After two unusually cold Marches in 2014 and 2015, this year's was at the other end of the temperature spectrum, finishing as the forth mildest and sixth driest on record.  It joined two other recent Marches in the top 10, from 2012 and 2010.  The month was 6.4 degrees above average, with five days in the 70s and eight in the 60s; ten days (from 3/10 onward) had mean temperatures that were 10 degrees or more above average.  Below is a quick analysis of the ten mildest Marches.

 

• 2016 knocked March 1973 out of the top 10

• Only three of the top 10 had any measurable snow and all had less than an inch.  This year's 0.9", which fell on two separate occasions, made this the "snowiest" of the mildest Marches.

• March 2016 also stood out among the others because it had five days in a row with lows of 32° or colder.  And then a few days later, on March 9, the temperature rose to 77° - the earliest date for a reading this warm (followed by a high of 79° the next day).  

• Three Marches had a day or two in the 80s.  However, one March, 2000, had no days in the 70s or 80s.

• Two of the top 10 were very dry - 2012 (0.96") and 2016 (1.17") while two were very wet - 2010 (10.69") and 1977. (7.41").

• Although March 1946 is the mildest overall, March 2012 had the mildest average low.

• March 1979 had the coldest reading of the ten mildest, a low of 20°.

 

 

 

 

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The Freakish Snow & Cold of March 1956, 1958, and 1967

 

 

Although many winters have a significant snowfall and a cold snap in March, it often happens in the first two weeks of the month, and is usually limited to one snow event and a few days of cold weather.  This post, however, looks at three years that fell within a twelve-year period in the middle of the 20th century that experienced freakish snow and cold in the second half of the month. 

 

1956 (March 12 - April 8)

During this four-week period 25" of snow fell and temperatures were 6.5 degrees below average.  There were snowfalls of 6.7" and 11.6" that occurred two days apart, on March 16-17 and March 18-19, and then a 4.2" snowfall occurred on April 8 (as well as two smaller snowfalls under two inches).  Up until these four wintry weeks just eight inches of snow had fallen for the entire winter.

 

 

1958 (March 14-21)

On March 14 there was a snowfall of 4.1" followed a week later (March 20-21) by a nor'easter that dumped 11.8" of wet snow.  (This storm paralyzed an area from Maryland, eastern Pennsylvania and much of New Jersey with 20-40 inches.)  And while temperatures in NYC were colder than average during both snowfalls, temperatures much of the time were above freezing.  This ended up being the snowiest month of the winter.

 

 

 

1967 (March 15-23)

During this nine-day period 15.4" of snow fell from three storms, and temperatures were 15 degrees below average.  On the 18th, the high/low was only 20°/10°, which was 27 degrees below average.  Then, on the morning of the 19th the low fell to 8° above zero, the latest date on record for a single-digit reading.  From late afternoon on the 15th until noon on the 20th the temperature was 32° or colder.  This brutal cold was followed by a 10" snowfall on March 22.

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Warming Trend: A Decade-by-Decade Analysis

 

Monthly temperatures for New York (Central Park) go back to 1869.  With this century-and-a-half treasure trove of data in front of me, I calculated each decades' monthly temperatures.  As I immersed myself in the data, a story emerged - New York was noticeably cooler before 1930, and every month's coldest decade occurred in that period.  A second story was that the decade of the 2010s became the warmest decade for eight months (April thru October, and December).  Other findings:

 

• Comparing pre-1930 decades with 1930 onward shows that March has warmed the most (+3.5 degrees), followed by February (+3.2).  The least warming has occurred in September (+1.4 degrees) and June (+1.5).

• The biggest difference in temperature between a month's coldest and warmest decade has occurred with February and March.  In the 1880s March's mean temperature was 35.4° degrees while it was 42.9° in the 1980s, a warm up of 7.5 degrees.  In February the pre- and post- temperatures were 29.4° and 36.3°.

• While March in the years between 1930 and 1999 was 3.5 degrees warmer than the six decades before 1930, in the 21st century it has been 4.5 degrees warmer.  June, July and October were just 0.2 degrees warmer than their respective months in the 1930-1999 period.

• Until the 2010s the warmest decade for September and October was the 1940s.

• In the first two decades of the 20th century February was colder than January by a significant margin (29.9° vs 32.3°).

• Worldwide, the first decade of the 21st century has been the warmest on record, but New York's warmest decade was the 1990s. (However, the 2000s had NYC's mildest Aprils and Novembers.)  

 

COLDEST & WARMEST DECADES BY MONTH
	Coldest		Warmest
		Mean		Mean
	Decade	Temp	Decade	Temp
January	1880-89	28.7	1990-99	34.8
February	1900-09	29.4	1990-99	36.3
March	1880-89	35.4	1980-89	42.9
April	1870-79	48.1	2010-19	54.2
May	1870-79	60.1	2010-19	64.3
June	1910-19	69.0	2010-19	72.2
July	1880-89	74.6	2010-19	78.8
August	1880-89	72.0	2010-19	76.4
September	1870-79	65.4	2010-19	70.5
October	1890-99	55.5	2010-19	59.2
November	1870-79	42.0	2000-09	48.6
December	1870-79	32.8	2010-19	39.8
Source: NOAA Local Climatological Data

 

TEMPERATURE TRENDS OVER THREE PERIODS
	Mean Temperature			Degrees Diff
	Before			2000-2019 vs
	1930	1930-1999	2000-2019	Before 1930
January	31.0	32.6	33.0	2.0
February	30.9	33.9	35.6	4.7
March	38.3	41.5	42.7	4.4
April	49.5	52.1	54.0	4.5
May	60.7	62.6	63.2	2.5
June	70.1	71.6	71.8	1.7
July	75.2	76.9	77.4	2.2
August	73.3	75.3	76.1	2.8
September	67.0	68.3	69.7	2.7
October	56.0	57.8	58.2	2.2
November	44.0	47.3	47.7	3.7
December	34.4	36.6	38.8	4.2
FULL YEAR	52.6	54.8	55.7	3.1

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When March is Colder Than December

 

Typically, the month of December is five degrees colder than March, but about every five years (based on records since 1960) March is colder.  2014 was one of these years, as March, the coldest in 30 years, was three degrees colder than December.  Of the 34 years (since 1869) in which March was colder than December, the most extreme was in 2015 when it was 12.7 degrees colder (that December was the mildest on record).  Here are some other tidbits ...

 

• Of the years in which March has been colder than December, both months had below average temperatures in five of them.  The last time this happened was in 1916.  And in 1982 and 2006, despite March being colder than December, both months were milder than average.

• The most consecutive years in which December was colder than March is fourteen, from 1942 thru 1955.  However, there have never been more than two consecutive years in which March was colder than December.  (UPDATE: This is no longer the case as March 2015 was also colder than the December preceding it.)  Finally, in the last two decades of the nineteenth century, March was colder than December in half of the years. 

• Interestingly, one of the coldest Marches on record, in 1960, wasn't colder than that year's December, which was also much below average.

 

LAST 10 YEARS WHEN MARCH
WAS COLDER THAN DECEMBER
	Mean Temp		Difference
	March	Dec.	March v Dec.
Average*	42.5	37.5	5.0
2015	38.1	50.8	-12.7
2014	37.7	40.5	-2.8
2011	42.3	43.3	-1.0
2006	43.1	43.6	-0.5
2001	39.6	44.1	-4.5
1996	38.9	41.3	-2.4
1994	40.7	42.2	-1.5
1984	36.7	43.8	-7.1
1982	42.0	42.8	-0.8
1971	40.1	40.8	-0.7
*1980-2010
GREATEST TEMP DIFFERENCE
(MARCH V DECEMBER)
	Mean Temp		Difference
	March	Dec.	March v Dec.
2015	38.1	50.8	-12.7
1984	36.7	43.8	-7.1
1891	35.8	42.3	-6.5
1923	36.8	42.0	-5.2
1885	30.6	35.7	-5.1
1911	34.7	39.4	-4.7
1888	30.0	34.7	-4.7
2001	39.6	44.1	-4.5

Weather Analysis: The First 60-Degree+ Reading of the Year

 

 

There are a number of ways to gauge how cold a winter has been: mean temperature; the number of days with sub-freezing highs or single-digit lows; streaks of days with below average temperatures; or a dearth of mild readings.  For instance, after the brutal winter of 2015 New York didn't experience its first 60-degree day until March 26.  That's more than seven weeks later than the average date for this occurrence (Feb. 3) - and the latest date since 1982.  Here are more interesting tidbits about the first reading of 60+:

 

• In the 19th century (1869-1899) the average date of the first 60+ reading in Central Park was March 8, and then between 1900-1970 the average date moved up to Feb. 23.  Since 1970 the average date has been three weeks earlier.

• Between 1900-1970 the first 60+ day occurred on March 1 or later in half of the years, but since 1971 it has occurred after March 1 just 20% of the time.

• Since 1900 the first 60-degree day has occurred on New Year's Day five times: 1919, 1966, 1973, 1979 and 2005.  (In 1966 the year's first 60+ reading followed 1965's last 60+ reading on New Year's Eve.)

• Looking at all years the latest date for the first 60+ reading was April 15, in 1877.  And nine other years had their first reading in the 60s between April 5 and April 13 (see chart below); the most recent year to have a date that late in 1970 (April 8). 

• Once every 10 years the first 60+ reading has occurred in the first three days of January, while once every 23 years the first 60 occurred on April 1 or later.

• In 2007, not only was the first 60-degree reading of the year very early (Jan. 5), it was followed the next day by the year's first high in the 70s (72°), the earliest ever. 

• In 1997 and 1998 the first 60+ temperature occurred on the same date, a very early Jan. 3.  And 1906 and 1907 had their first 60s on Jan. 4 while 2017's and 2018's  was on Jan. 12 (in 2020 it fell on Jan. 11).  At the other end of the spectrum, 1962 and 1963 both shared March 25 as the date of their first 60.

• For four years in a row, 2005-2008, the first 60-degree reading occurred in the first nine days of the year.

• In 1943, the year's first 60-degree temperature, 63°, came just five days after the morning low was 8° below zero. (And in 2022, the first temperature in the 60s, 68° on 2/17, was three days after the low was 16°). 

• The coldest temperature to occur on the same day as the first reading of 60+ was in the winter of 1957 when an Arctic front knocked the temperature down to 20° after the mercury reached 60° earlier in the day (on Jan. 23).

• The biggest jump in temperature from the day before the first 60+ reading was 25 degrees, in 1954, when the high jumped from 44° to 69° the next day.  The biggest increase in temperature the day following the first 60+ was 21 degrees, and it happened in 1917, when the high reading the day after rose to 83°.  Lastly, the biggest drop in temperature after the first 60+ was 33 degrees and it happened in three years: 1957 (from 60° to 27°); in 1939 (62° to 29°); and in 1913 (63° to 30°).

• The date of the first 60+ reading in five years was also the date of the first 70+ reading: in 1987 (March 7); 1969 (March 18); 1964 (March 5); 1963 (March 25) and 1893 (April 1).  Nine other years had their first 70+ reading the day after the first 60+, the last time being in 2007.

 

Snowfall Analysis: New York's Snowiest Consecutive Months

 

The snow that piled up in New York during the winter of 2014 made it one of the ten snowiest on record (going back to 1869).  The bulk of the 57 inches fell in January (19.7") and February (28.8").  Their combined total of 48.5" is the second greatest amount of snow to fall in back-to-back months.  Only the winter of 2011 had a combo with more as December picked up 20.1" and January saw 36.0". 

 

Three of the winters found on the chart below had 20" or more of snow for both of the months: Jan/Feb 1978, Jan/Feb 1996 and Dec 2010/Jan 2011.  And three winters make two appearances: 1996, 2010 and 2011.  (If March 2014 sees nine inches or more it will also have two slots on the list.)

 

NEW YORK'S SNOWIEST BACK-TO-BACK MONTHS
(Since 1869)
Months	1st Month	2nd Month	Combined
Dec 2010/Jan 2011	20.1"	36.0"	56.1"
Jan/Feb 2014	19.7"	28.8"	48.5"
Jan/Feb 1996	26.1"	21.2"	47.3"
Dec 1947/Jan 1948	29.6"	15.3"	44.9"
Jan/Feb 1978	20.3"	23.0"	43.3"
Jan/Feb 1923	24.5"	18.8"	43.3"
Feb/Mar 1967	23.6"	17.4"	41.0"
Feb/Mar 2011	36.0"	4.8"	40.8"
Dec 1904/Jan 1905	21.6"	18.4"	40.0"
Feb/Mar 1896	9.5"	30.5"	40.0"
Jan/Feb 2010	2.1"	36.9"	39.0"
Feb/Mar 1914	17.4"	21.5"	38.9"
Jan/Feb 1994	12.0"	26.4"	38.4"
Dec/Jan 1996	11.5"	26.1"	37.6"
Dec/Jan 1893	27.0"	10.6"	37.6"
Dec 2003/Jan 2004	19.8"	17.3"	37.1"
(Analysis of data from www.NWS.NOAA.gov)