October 2021 Weather Recap: 6th Mildest October Ends With Soaking Rains

 

 

After unprecedented rainfall in July, August, and September (each month had more than ten inches), it appeared a respite was in store during October, as the first half of the month was the driest since Oct. 2000, with just 0.15" of rain measured.  However, these dry conditions came to an abrupt end in the last week of the month, as 4.71" was measured - the wettest last week of October on record (and eight of the last nine days had measurable rainfall).  Much of the week's rain was produced by a nor'easter on the 25th-26th that dumped 3.69" of rain. 

 

 

The month's other storyline was its mild nighttime temperatures.  There was a record streak of lows in the 60s (13 days), which was also the month's total number of days with lows in the 60s, tying Oct. 1879 for the most on record (the average number of lows of 60+ in October is 4).  Lows during the first 12 days of the streak were in the narrow 60°-62° range; Day 13's low was 63°.  Of the eight longest streaks of lows in the 60s/70s in October, this year's record streak was the coolest.

 

 

Overall, the month was 4.1 degrees above average, and became the sixth mildest October on record (it ranked fourth for average low, and tied for 19th for average high).  17 days were five degrees or more above average; seven days had  below average mean temperatures.  The most above average day was 10/15, which was thirteen degrees warmer than average (high/low of 79°/63°); the most below average day was 10/1 , which was five degrees below average (67°/51°).

 

Temperatures during October ranged from 47° (on 10/19, 10/24, and 10/29) to 79° (on 10/15).  Only three other Octobers have had a smaller temperature range: 1977 (30 degrees); 2004 (31 degrees); and 1894 (31).    This mirrored September, which had a 31-degree variation, and was tied for third smallest variation.

 

In an oddity, there were six days with temperatures stuck in the 60s - the most on record for any month.  They occurred in three pairs, and were concentrated in the nine-day period between Oct. 3-11.  This narrow temperature range was largely due to persistent overcast skies.

 

The season's first low chillier than 50° was reported on 10/18, which was the second latest day for this occurrence (latest is 10/20).  Additionally, the month's chilliest reading of 47° (reported on three days), was the mildest chilliest reading on record for October (on average, the coldest reading in October is in the upper thirties). 

 

Here are previous recaps of October's weather:

2020

2019

2018

2017

2016

October 2020 Weather Recap: 'Mother Nature' Dresses Up as 'Jack Frost' for Halloween

 

October 2020 was slightly milder and wetter than average in New York.  The month's first week-and-a-half was uneventful, with just 0.06" of rain.  Then three significant rain events soaked the City, each bringing more than an inch of rain: 1.30" fell on 10/12-13; 1.36" on 10/17 and 2.17" on 10/29-30.  The first and third rainmakers were from remnants of hurricanes Delta and Zeta.  The month ended up with 5.05" of rain, 0.65" above average.  Overall, the month was one degree above average, making it the 11th October in a row that was milder than average.  The low was nearly two degrees above average while the high was just about average (+0.1 degree). 

 

Until the end of the month the chilliest reading had been 44°, which would have been one of the mildest readings for this distinction in October (October 1946's and 1971's coolest reading was 45°; October 2007's was 44°; last October's was 43°).  But then a shot of Arctic air followed the rainstorm of 10/29-30 and Halloween morning dawned with a low of 32°, the coldest reading in October since 1988.  This was three weeks earlier than the average date of the first freezing or colder reading in Central Park.

 

 

The month's mildest reading was 74° (on 10/7), which was the coolest warmest reading in October since 2009, which also had a mildest reading of 74° (October 2009 was the last time the month was chillier than average).  The last time the warmest reading was cooler than this was in 1987, when it was 72°.  (By contrast, last October's warmest reading was a sizzling 93°.)  There were just six days with highs in the 70s (the October average is nine), none of which occurred back-to-back.  This was just the third time this has happened in October in the past 100 years.  And this October was the only one of the three that was above average temperature-wise.

 

Although the month was one degree milder than average, both the warmest and chilliest readings of October were six degrees cooler than what the average warmest and chilliest readings are in October.

 

Finally, there were just eight days with mean temperatures five degrees or more above average, and four days that were five degrees or more below average.  The lengthiest streak of days that were five degrees or more above average was five (10/20-24); this streak was nine degrees above average (high/low of 69°/58°).  There were no extended periods of significantly chillier than average temperatures, but the last two days of the month were twelve degrees below average (high/low of 47°/34°).

 

 

Here are previous recaps of October's weather:

2019

2018

2017

2016

 

 

 

 

A Reading in the 90s Makes October 2019 Memorable in New York

 

Although above average rainfall characterized October 2019, a day of sizzling heat at the beginning of the month is likely what many New Yorkers will remember.  After having no days in the 90s in September, the high on 10/2 was a torrid 93°, 24 degrees above average - and the first 90-degree reading in October since 1941.  (The high the next day, however, was thirty degrees chillier.)  As for the rain, 6.15" was measured, the most in October since 2006, and the second rainiest month of the year (May had 6.77").  A little more than half of the month's rain fell on two days: on 10/16, when 1.83" fell, and 10/27 (1.38").

 

The month was three degrees warmer than average and was the 24th mildest October on record (but it ranked 12th for average low).  And although it had just a few days with highs of 70° or warmer or lows in the 60s, the month also had very few days with highs in the 50s or lows in the 40s (the chilliest reading was 43° on the 19th).  Similar to September, October ended with 11 days in a row with above average readings (averaging six degrees above average).  Temperatures between 10/3-20 were average while the other 13 days of the month were seven degrees above average.

 

In the years since 1900 three out of four Octobers have had their chilliest readings in the 30s or 20s.  October 2019 joined only five other Octobers whose chilliest lows were 43° or milder.  (The mildest reading to be the chilliest October low is 45°, which happened in 1945 and again in 1971.)  The typical chilliest October temperature is around 38° (fourteen Octobers since 1900 had chilliest readings of 32° or colder; the last time it occurred was in 1988).

 

 

The low on Halloween was 60°, 15 degrees above average.  It joined 10/1 and 10/2 as the only days in October with lows in the 60s.  The high of 71° on 10/31 was the warmest reading on the holiday in ten years, when the high was also 71°.  It was also the mildest reading since 10/14.  (And although 10/31's high of 71° was 22 degrees cooler than 10/2's, its low was just three degrees lower.)

 

 

Finally, October's plentiful rainfall followed a very dry September, in which just 0.95" was measured.  And while this was a decided contrast, it wasn't nearly as extreme as Sept/Oct 2005 when  October saw 16.73" after a paltry 0.48" in September; April/May 2007, when April had 13.05" and May had just 1.88"; and Aug/Sept 1882, when September had 16.85" and August only 1.14".

Here are links to other October recaps:

2018

2017

2016

 

 

 

October 2018 Weather Recap: Started Out Like September, Ended Like It Was November

 

Although October wasn't far from average in terms of its overall temperature, few would think of it as merely average as temperatures in the first eleven days of the month, comparable to the start of September, were followed by nearly three weeks of temperature more like early November.  Through the 11th temperatures were ten degrees above average (high/low of 75°/65°), then the rest of the month was nearly twenty degrees colder (57°/45°), and four degrees below average.  Another contrast was between the departure from normal of the month's average high, which was a titch below average (-0.3 degrees), and the average low, which was nearly two degrees milder than average (+1.9 degrees).  And despite it being 0.8 degrees above average, this was the chilliest October in seven years.

Additional points of interest:

• Similar to August and September, the difference between October's average high and low (i.e., diurnal variation) was one of the smallest on record for October - 11.6 degrees (the average is 15.4 degrees).  In the past 100 years only October 2012 had a smaller variation.

• Just a year after the latest date for a low in the 70s occurred (on 10/9) a new mark was set this year when a low of 71° (five degrees warmer than the average high for the date) was reported on the 10th.

• The month was well above average in terms of days with lows of 60° or milder (eleven).  Only October 1879 (thirteen), 2012 (warmest October on record) and 2007 had more lows of 60+.  And this October's eleven days were consecutive (Oct. 1-11), which set a new October record and included five days in a row with mean temperatures that were ten or more degrees above average.  However, despite these balmy conditions just one day, 10/10, had a high in the 80s (80°).

• During the chilly portion of the month there were a dozen days with highs in the 50s, the most since 2009 (the typical number is eight).  And the number of lows in the 30s was three, the most since 2011 (the chilliest reading was 38°).

• The high of 64° on Halloween (five degrees above average) was the month's mildest reading since 10/15 and the first Halloween to have temperatures in the 60s in five years.

• Finally, much of October's 3.59" of rain (the smallest amount in five years) came from the remnants of catastrophic hurricane Michael on 10/11-12, which brought 1.27", and a nor'easter on 10/27 that produced 1.29".  On 10/20 the year's total precipitation passed 50 inches, and by the end of the month 51.42" had been measured, which is close to two inches more than what falls in a typical year.  This ranks as the the ninth greatest amount of precipitation (since 1869) through the end of October.

Here are recaps of previous Octobers:

2017

2016

Lacking Autumn Feel, October 2017 Becomes Warmest on Record

The unseasonably mild fall weather that began in the middle of September persisted throughout October, resulting in a month that was 7.2 degrees warmer than average.  With an average high/low of 71/57 this was the warmest October on record, finishing ahead of 2007 and 1947 by 0.5 degree.  14 days were 10+ degrees above average; 19 had highs of 70° or warmer - second only to October 1947's 22; and just three had chillier than average readings.  Until the end of the month it appeared October would also be characterized by a lack of rain as less than an inch fell in the first four weeks.  However, that storyline ended on 10/29-30 when a nor'easter drenched the City with 3.28" of rain - more rain than the previous 60 days.  This was New York's biggest rainstorm in three-and-a-half years (since 4/30/14 when 4.97" fell).  Other highlights: 

 

• The record for the latest date with a low in the 70s was established and then re-established on consecutive days (10/8 and 10/9).  Interestingly, despite these tropical readings, neither day had a high in the  80s.

• The month's chilliest mean temperature occurred on 10/17, with a high/low of 58/42 (six degrees below average).  The chilliest high, 57°, occurred on Halloween.  Only two other days had lows below 60°.  The month had a dozen days with lows of 60° or warmer, tying Oct. 2007 for the most in the years since 1900.

• The three days with below average mean temperatures were widely separated - on 10/1 (three degrees below average), 10/17 (-6 degrees) and 10/31 (-2 degrees).

• The warmest stretch of the month was a seven-day period, 10/5-11, which was 14 degrees warmer than average.  Each day had a high of 77° or warmer and all seven days were 10+ degrees above average.  The average high/low of this week was 80/67, comparable to late August.

• Although it reigns as the mildest October on record, eleven other Octobers had more days with highs of 80°+ (this year's had four).  The warm days of these eleven months were balanced by cold periods that this October didn't experience.  Speaking of which, this October tied October 1984 and 1949 for the fewest days with lows below 50° - just five.

• For the first time since 1990 October was milder than May.  Typically, May is five degrees warmer but this year it was three degrees cooler.

• Finally, October joined four other months that, since the beginning of 2015, became the warmest on record: Feb. 2017, Dec. 2015, Nov. 2015 and Sept. 2015.  And five other months became the second or third warmest.  (An outlier was Feb. 2015, which was the third coldest on record.)

 

 

 

 

 

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October 2016 - 16th Month In A Row With Above Average Temperatures

The first half of October 2016 was uneventful, with average temperatures and little rainfall (0.78" thru 10/16).  Then an out-of-the blue, three-day warm spell occurred Oct.17-19, with each day's high topping 80° (by contrast, the first half of the month had just three days in the 70s, none higher than 75°).  This was only the third time in the past 100 years that October had three or more days in the 80s after Oct. 15 (the other two Octobers were in 1963 and 1947).  The warmest of these days, Oct. 19, had a record high of 85°.  (One week later the temperature dropped to 38°.)  Following this touch of summer, two rainstorms in a six-day period brought 1.40" (10/21-22) and 1.41" on (10/27) - the rainiest stretch since three rainstorms delivered 3.42" during the last week of July.  Finally, on 10/30 the temperature climbed to 76° one day after a low of 39° (but Halloween's high would be twenty-two degrees chillier). 

 

All in all, the month was 1.9 degrees milder than average, making this the sixteenth month in a row with above average temperatures, building on the record streak set in September when the fifteenth month in a row occurred (breaking the previous record of 14 months set in 2011-2012).  This was also the seventh October in a row that was milder than average.

 

    

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October's First Autumn Chill

 

I don't know about you, but I find adjusting to the season's first chilly temperatures in the fall a more challenging than adjusting to warm weather in the springtime.  In the fall of 2015 the temperature fell to 35° on the morning of Oct. 19, which was the earliest it was this chilly since 1976, when the low on the same date was 34°.  Mornings in the 30s in October occur infrequently in New York City, with a typical October seeing just two such days.  The average date for the first low in the 30s is Oct. 23.  It's happened as early as Sept. 30 (in 1912) and as late as Nov. 15 (1938).  On average, October's coldest reading is 38°, with the coldest being 28° in 1936.  The mildest chilly reading, 45°, occurred in 1971 and 1946 (more recently, October 2004's chilliest reading was 44°). 

 

The greatest number of lows in the 30s has been nine, in 1925.  One in eight Octobers have had lows of 32° or colder; however, the last time it happened was in 1988 (the coldest temperature in recent years was 33° in 2011).  At the other end of the temperature spectrum, one in four Octobers have had no readings in the 30s (most recently in 2017, 2014 and 2013).  Here are some other observations:

 

• Two periods have had considerably more 30-degree days than other years.  The years between 1922-1940 averaged 3.9 30-degree days in October.  This followed the years 1910-1921, which averaged only 1.4 such days.  Then there were the years between 1964-1988, which averaged 3.2 chilly lows; since then the average has been half that, 1.6.

• October 1974 and 1925 were noteworthy for having three days in a row with lows of 32°  or colder.  And October 1940 and 2011 distinguished themselves by having five days in a row with lows in the 30s. 

• The most consecutive years with Octobers that had no readings below 40° is three: 1994-1995-1996.

 

 

• The second latest date for the first reading in the 30s, Nov. 13, 1946, was sandwiched between two years with the earliest dates for this occurrence - Oct. 1, 1947 and Oct. 4, 1945.

• After having the earliest temperature in the 30s on record, Sept. 30 in 1912, October had none.

• Finally, there have been two high temperatures in the 30s in October: on Oct. 26, 1962 (39°) and on Oct. 30, 1925 (38°).

 

 

 

 

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Today in New York Weather History: October 17

 

1938

Today's high was a sizzling 90°, the latest date on record for a 90-degree reading - a record that still stands.  This high was 27 degrees above average.

 

2014

This was the tenth day in the past five weeks to have a high of 71°.  On the first day with this high, 9/14, the reading was four degrees below average, but when the mercury reached 71° today it was eight above average.

 

2016

After nine days in a row with highs in the seasonable 60s, today's high jumped to 81°, the first 80-degree reading since 9/23, and the first reading in the 80s in October in three years. This was also the 100th day this year to have a high of 80° or warmer, just the seventh year to reach this threshold.  It came a year after the record for the most 80-degree days was set - 114.

2021

Today was the first day since 10/1 to have a below-average mean temperature, as the high/low of 61°/51° was one degree below average.  (The low on 10/1 was also 51°.)

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Autumn Warm Spells - When Summer Keeps Hangin' On

 

Although the general public often refers to warm spells in the fall as "Indian Summer," most occur before the first frost arrives (which, compared to the suburbs, comes weeks later to Manhattan/Central Park).  This analysis goes back to 1950 and looks at warm spells that have occurred mostly in October and November (with some beginning in late September).  For my purposes I focused on those that were at least four days in length.

 

 

LENGTHIEST

Two-thirds of the years since 1950 have had warm spells of four or more days (including the ten of the eleven years between 2010 and 2020).  Seventeen years had two or more, with 1953 experiencing four.  There have been ten warm spells that lasted ten days or more, the most recent being in the autumn of 2006.  The lengthiest was twenty-one days, which has occurred twice, in 1959 and 1984.

 

MOST ABOVE AVERAGE

There have been thirty-nine warm spells in autumn that averaged ten degrees above average or more (based on daily mean temperature).  The five-day heat wave of Sept. 22-26, 1970 was the most above average, +18 degrees, with four of the five days experiencing highs in the 90s. 

 

LENGTHIEST AUTUMN WARM SPELLS
(SINCE 1950)
		# of	Average		Degrees
Year	Dates	Days	High	Low	Above
1959	Sept 21-Oct 11	21	81	65	+11
1984	Oct 11-31	21	70	57	+ 8
1973	Sept 27-Oct 15	19	74	57	+ 6
1995	Oct 2-14	13	76	58	+ 7
1986	Sept 23-Oct 4	12	79	64	+ 8
1979	Nov 18-28	11	65	52	+14
1994	Oct 30-Nov 9	11	69	52	+ 9
1990	Oct 6-15	10	80	65	+13
2006	Nov 8-17	10	63	53	+10
1970	Oct 6-15	10	74	60	+ 9
WARM SPELLS WITH GREATEST DEPARTURE
FROM AVERAGE
		# of	Average		Degrees
Year	Dates	Days	High	Low	Above
1970	Sept 22-26	5	90	72	+18
1950	Oct 29-Nov 2	5	79	58	+17
2020	Nov 6-11	6	73	58	+16
1979	Oct 20-23	4	81	65	+16
1991	Nov 19-23	5	67	54	+16
1954	Oct 10-15	6	82	64	+15
1961	Nov 3-6	4	73	59	+15
1963	Oct 24-27	4	79	57	+15
1979	Nov 18-28	11	65	52	+14
1971	Oct 26-Nov 3	9	72	60	+14
1975	Nov 2-10	9	72	57	+14
2007	Oct 3-9	7	82	66	+14

 

 

 

 

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80-Degree Weather in April and October

 

On average, temperatures reach the 80s, or hotter, on 1.4 days in April and 1.1 in October (since 1970).  Interestingly, despite the higher likelihood in April, its average high temperature is a few degrees cooler than October's.  In the years between 1970 and 2019, April has had about 25% more 80/90-degree days than October (72 vs. 57 days).  However, this disparity didn't start until 2000.  Between 1970 and 1999 the two months were relatively close (35 days in the 80s in April vs. 31 in October), but since 2000 April has had 37 such days while October has lagged behind with 26.

 

The greatest number of 80-degree days to occur in April is five, which happened twice, in 1985 and 2002.  October 1990 had six 80-degree days and five in 1995 and 2007. The most years in a row without an 80-degree temperature being reported in April is three; the same holds true with October.  However, while the most consecutive years with 80-degree readings (or warmer) in October is four (2016-2019), April, has had a streak of thirteen years (2001-2013).

 

 

Since 1970 thirteen of April's days above 80 degrees have been in the 90s, but just one such day has occurred in October (it was in 2019 and was the first high of 90+ in October since 1941). 

 

 

Finally, there have been ten 80-degree days before April 1, but just one after November 1.  (March and November totals aren't included in this analysis.)

 

 

 

 

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