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Autumn Warm Spells - When Summer Keeps Hangin' On

Sheep.meadow

 

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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Low Temperatures of 70 Degrees or Warmer: An Analysis

70s

 

A typical year in New York sees 37 days with lows in the 70s or 80s, with the first coming around June 4 and the last on Sept. 11.  (This is nine days longer than the "season" for 90-degree high temperatures.)  In the period 1970-2020, the number of these days has ranged from just 14 in 1992 to 60 in 2005  (2010, the year with the hottest summer, had 55.)  The longest streak of lows of 70°+ is 22 days and it occurred twice, in 1980 and 2010.  There was also a 21-day streak in 1988.  The longest streak of days with lows of 75°+ (which we get eight of each year) occurred in the summer of 2013 when there were eight consecutive days in mid-July. 

 

MOST & LEAST 70-DEGREE LOWS
(Since 1970)
       
MOST   Days First Last
2005 60 June 8 Oct 7
2015 56 May 1 Sept 29
2010 55 June 4 Sept 28
2018 54 May 3 Oct 10
1980 54 June 25 Sept 22
       
Average 37 June 4 Sept 11
       
LEAST   Days First         Last
1992 14 June 8 Sept 9
2009 18 July 16 Aug 26
2000 23 May 8 Sept 12
1975 23 June 19 Aug 26
1976 24 April 18 Aug 28
       

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Today in New York Weather History: April 14

 

1880

Today's high of 80° came just two days after a record low of 26° (since eclipsed in 1976).  This was the first reading above 64° since 3/5 (when it was 72°).

1940

A trace of snow was reported for the 33rd time this snow season, the most ever (later tied in 1944-45).  Today's high/low was 41°/30°.

 

Trace

1966

This was the fourth day in a row with a low of 39° (five degrees below average).  However, all of the days had different highs, with three in the 57°-60° range and one with a high of only 44°. 

1979

It was a rainy and chilly Easter Saturday.  1.10" of rain fell (ending late in the afternoon) and the high/low was 45°/40°; the high was nearly twenty degrees below average. 

2014

This was the fourth day in a row with highs in the 70s.  The average high during these days was 75°, fifteen degrees above average.

 

Clipart_sun_with_glasses

2018

After the temperature peaked at 77° in the middle of the afternoon, a "back-door" cold front moved through, and by midnight the temperature had fallen to 44°.  This was the greatest drop in temperature since 1/13, when it plummeted from 58° to 19°.  (It was also the second biggest drop in more than four years.)

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A History of Mild December Temperatures in New York

Clipart_meltingsnowglobe

 

 

  • Since 1970 the warmest reading in December has averaged 60°.  Between 1970-1999 it was 58°; since 2000 it has been 64°.
  • December 1998 and 2001 each had two days with 70-degree highs. And every day of the first week of December 1998 had highs of 60° or warmer (including the two 70-degree highs).
  • In eleven years since 1970 the mildest reading in December has occurred after the first day of winter.
  • Since 1970 six years have had mildest December readings of 55° or lower.  The coolest maximum was 53° in 1989.
  • In 2004, 2005, 2006 and 2015, December's mildest reading occurred just before Christmas (12/23, 12/24, 12/23 and 12/24, respectively).
  • December 2013 is just one of four Decembers since 1970 that had a warmer reading than November.  The other three were in 2006, 1998 and 1983.   
  • Decembers with very mild readings don't preclude significant snowfalls.  For example, 2013's 71-degree reading on 12/22 followed a wintry 10-day period between 12/8-17 which saw 8.6" of snow.  In 1984 a 70-degree day on 12/29 came just two days after 4.8" of snow fell; in 1990 a snowfall of 7.2" came five days after a high of 66° on 12/23; and in 2008 a 4.5" snow event followed a high of 67° five days earlier on 12/15.

 

Clipart_tropical_santa  

 70 in December

 

December Chilliest Max

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80-Degree Weather in April and October

Sunny_day_nyc

 

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).

 

Warm_weather_april

 

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). 

 

Clipart_hotthermometer

 

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.)

 

Chart - 80s in Apr and Oct

 

 

 

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Unbearably Warm Summer Nights in New York

Hot_nights_nyc_firehydrant

 

It used to be that New York's most stifling overnight temperatures in the summer fell into the upper 70s - but lows of 80° or warmer were few and far between.  However, this began to change in the late 1970s.  Since then, lows of 80° or warmer have occurred 38 times (thru 2020) - still infrequent, but no longer unheard of.   As Sandy and Danny sang to each other so famously in Grease, "Oh, those summer nights!"

 

  • Looking at the years from 1950 onward, only 1952 and 1957 registered 80-degree lows before 1978.  But since 1978, nineteen years have had lows of 80+.  To put it another way, there were no 80-degree lows in the twenty year period between 1958-1977, but they've occurred every two or three years since 1978.
  • The most 80-degree lows were experienced during the summer of 2002, when there were four.  Four other summers have each had three such stifling readings: 2013, 2010, 1988 and 1980.
  • The warmest low temperature, 84°, has occurred four times, most recently on July 22, 2011 and July 15, 1995 and twice during the summer of 1908.  (2011's high was two degrees hotter than 1995: 104 vs 102; both days in 1908 had highs of just 93°).  Interestingly, on the day of New York's hottest temperature on record, 106° on July 7, 1936, the morning low was 77°.  Therefore, July 22, 2011 is the day with New York's hottest mean temperature (94°).

 

84LumberLogo

 

  • With the exception of 1952, when an 80-degree low occurred on June 26, all other 80-degree lows have occurred in July or August.  The latest date for such a warm low is Aug. 30, 2018.  This broke the previous record, in 1985 and 1988, by 14 days.
  • The summer of 1995 reported the most low temperatures of 77° or warmer, eleven - one which was 84° and the remaining ten were between 77°-79°.  It was followed by 1999 and 2002, with ten.
  • The biggest rise in temperature on a day with a low of 80° or warmer was 22 degrees, which happened on July 10, 1993 (102°/80°) and was equaled on July 6, 2010 (103°/81°).  The smallest rise in the past 100 years is eleven degrees, which was reported on Aug. 30, 2018 when the high/low was 92°/81°. However, there have been seven even smaller variations in the years before 1911, with the smallest being seven degrees, which occurred during the summers of 1906 and 1908, both with a high/low of 87°/80°.

 

Chart - smallest diurnal variation on hot days
 

  • A low in the upper 70s or warmer doesn't guarantee the afternoon high will soar into the 90s.  There have been fourteen instances where the high has stayed below 90° (three of them occurred in 2015, two in 2016).  The two days that failed to reach 90° with the warmest low occurred on July 26, 1979, when the high struggled to 87° after a low of 79°, and on July 15, 2016 when the high reached 88° after the same low.  The smallest diurnal variation when the low was 77° or warmer was seven degrees - and it also happened during the summer of 1979.  On Aug. 4, under a thick haze, the high struggled to reach 84°.
  • Twelve years since 1950 haven't had a low of 77° degrees or warmer.  The coolest "warmest" low was 74° degrees, which occurred in the summers of 1996, 1976 and 1962.
  • Between 1950 and 1977 the typical year had twenty-eight days with lows of 70° or warmer.  Since 1978 the average number of such day has risen to thirty-seven.  The most was 60 days in 2005; the fewest was eight in 1962.

 

80-Degree Lows
(1950-2012)    
  Daily Minimum Temp
Year 80+ 77-79 Total
2002 4 6 10
2010 3 5 8
1988 3 5 8
1980 3 3 6
2011 2 2 4
1999 2 8 10
1993 2 2 4
1952 2 2 4
2006 1 5 6
2005 1 6 7
2001 1 3 4
1995 1 10 11
1985 1 2 3
1982 1 1 2
1981 1 4 5
1978 1 1 2
1957 1 1 2

Note: Chart does not yet include 2013's three 80-degree lows, 2015's one or 2016's two.

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Today in New York Weather History: June 5

 

1927

Today's high of 81° was the first in the 80s (or warmer) since the 90-degree high on 4/20, nearly seven weeks ago.

1945

Today and the previous two days were unusually chilly, with periods of light drizzle, fog and clouds, and northeasterly winds.  The highs and lows for the three days were: 53°/50° on June 3; 52°/49° on June 4; and 55°/47° today.  Whereas the low temperature during these days averaged ten degrees below average (comparable to late April), the average high of 53° was twenty-three degrees below average (comparable to late March).

 

The50s 1992

2.80" of rain fell today, a record for the date.  Most fell during the afternoon and early evening, with the greatest amount pouring down between 6-7 PM, when 0.60" fell.

 

Singing_in_the_rain

2010

This morning's low was a sultry 76°, sixteen degrees above average, and what a typical high should be for the date.  The afternoon high hit 88°.

2012

Today's high/low of 64°/51° was ten degrees cooler than average, just the third time this year that the daily mean temperature was this much below average (the last time it happened was on Jan. 15).  And the AM low was the chilliest in June in three years.

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Today in New York Weather History: June 2

 

1928

Today's high of 83° was the second 80-degree day of the year and came nearly two months after the year's first, on April 5 (a record for the date).  In the years since 1900 (thru 2021) this 57-day hiatus is the longest on record.

1946

Two days after a summery high of 86°, today was more than 30 degrees colder, along with a soaking rain of more than two inches (six days after another two-inch rainfall).  Today's high was just 52°, twenty-four degrees below average and came one year after an equally chilly three-day period from June 3-5 that saw an average high/low of 53°/49°.     

1967

Like yesterday, today's diurnal variation was 30 degrees, but today's high/low of 88°/58° was ten degrees warmer.  Both days featured clear skies.

1988

Today's high of 63° was twenty-seven degrees cooler than yesterday's high of 90°.

 

Arrow_pointing_down

1997

An all-day rain produced 0.99", more than half of the month's total (1.93").  This was the first measurable rainfall on this date in 10 years.

2005

Although it was on the cool-ish side (high/low of 69°/54°), skies were clear and it was a beautiful evening for an after-work excursion around Manhattan on the Forbes yacht.

2006

A severe thunderstorm struck shortly after lunchtime on Friday and dumped 1.73" in an hour (2:35-3:35 PM).  During this hour, 0.54" fell in five minutes, and 1.02" in ten minutes.  Total rainfall for the day was 2.79", a record for the date.  

 

Thunderstorm_over_manhattan

2007

This was the tenth day in a row with a high temperature of 80° or warmer.  The average high during these days was 86°, twelve degrees warmer than normal.

2011

The past ten days were nice and balmy, with sunny skies predominating.  Afternoon highs averaged close to 84°,  ten degrees above average.

 

Clipart_stylized_smilingsun

2013

A day that was very warm (upper 80s) and humid was capped off by a late night thunderstorm with vivid lightning that dumped a half-inch of rain in just fifteen minutes (10:25-10:40).  

2015

One day after a chilly high/low of 58°/51°, today was even chillier.  With a high/low of just 55°/50° this was the chilliest day in June since June 2, 1946 (52°/48°).  Today's high was twenty-three degrees below average.  Drizzle and light rain fell throughout the day, bringing Central Park's total rainfall since 6 PM on 5/31 to 2.55" - more than what fell during the previous sixty days. 

2019

A nighttime thunderstorm dumped 0.78" of rain in the 30 minutes between 9:45 and 10:15.  This was the greatest amount in such a brief period so far this year.  Central Park appeared to be the bulls-eye for the heaviest rain as Newark Airport reported 0.31", LaGuardia had 0.30" and JFK just 0.03".  (And at Yankee Stadium there was no rain delay for its game).      

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Looking Back at New York's Weather: June 1

 

1887

After experiencing what, at the time, was the driest May on record (0.34" was measured; it's now ranked second after May 1903), June began with a rainfall of 2.60", which was more than what fell in the previous six weeks.  It was also a record for the date (which still stands).

1959

Today's chilly high of 64°, under mostly overcast skies, followed a five-day warm spell at the end of May that had highs that averaged 87° (13 degrees above average).  Today's conditions were the result of a "back-door" cold front that moved in from New England last night. 

1967

Today's temperature jumped 30 degrees, from 48° to 78°.  This is the warmest reading for a day in June with a low in the 40s.

1977

Rain fell on this date for the sixth year in a row.  This year's rain amounted to 0.16" and fell mostly between 11 AM-1 PM.

1986

Today was the 17th consecutive day with above-average temperatures.  During this two-and-a-half week period temperatures were nearly eight degrees warmer than normal (high/low of 81°/63°).  On this last day of this extended warm spell, the high reached 90°.

 

Clipart_simplesun

1987

This was the last day of an early four-day heat wave.  Highs on these days were: 96°-97°-94°-93° (today), for an average of 95°, twenty degrees above average.

1989

For the fourth year in a row the high on June 1 was in the 90s.  (It wouldn't hit 90° on this date again until 2011.)  Today's high of 91° was also the first 90-degree temperature of the year.  Last year's first 90-degree day occurred one day earlier.  

1991

Fourteen of the past twenty-one days had temperatures 10+ degrees above average.  The mean temperature during these three weeks was nine degrees above normal (high of 84°/low of 63°).

2006

0.99" of rain fell during an evening thunderstorm, with 0.73" falling between 8-9 PM.  Before the storms developed, the weather was warm and humid, with a high/low of 86°/64°, nine degrees above average.

 

Clipart_thunderstorm2

2011

Today had the first 90-degree reading of the year, just a few days after the typical date for the first 90.

2013

For the third day in a row the afternoon high, under sunny skies, reached 90°.  This was New York's earliest heat wave since a three-day streak in April 2002.

2014

It was a glorious day for the first day of June as skies were sunny, temperatures rose into the upper 70s, and the humidity was very low.

2015

After a week of temperatures in the summery mid-80s, today was 30 degrees chillier, with light rain, drizzle and fog.  (Similar to the conditions on June 1, 1959.)  Today's high in the 50s was chillier than any day in May - the first time for this occurrence.

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Today in New York Weather History: May 28

90degrees

 

May 28 is the average date of New York's first 90-degree temperature.  Since 1970 it's happened as early as April 7 (in 2010) and as late as July 14 (in 1985).  This date is more than two weeks earlier than what the average date was in the years before 1930, which was June 14 (1870-1929).

 

1973

Today was Memorial Day and 0.59" of rain fell during the morning.  The afternoon remained overcast and the high reached 70°, five degrees below average.  

1977

Today's high was 92°, the ninth day in a row with a high of 80° or warmer (and twelfth of the past thirteen days).  During this warm spell, the high averaged 83°, nine degrees above average.

1984

For the second year in a row more than an inch of rain fell on Memorial Day.  Last year it fell in the early morning and evening.  This year it fell during the afternoon.

 

Singing_in_the_rain

1985

0.54" of rain fell in 30 minutes between 5:41-6:11 PM.  0.93" fell during the entire evening.

2012

Today was Memorial Day and for the seventh consecutive year the holiday had a high in the 80s.  Today's high was 89°, tying 1999 and 1991 as the hottest Memorial Day since 1969, when it was 91°.  Today also had the year's first 70-degree low, about a week earlier than average, and the earliest since 2007 (when it occurred on May 26).

 

Hot_sun

2013

Today's 0.52" of rain was the last rainfall of the month, bringing the total to 8.00" (the wettest May since 1990).  This was just the sixth month in the past 100 years to have a monthly precipitation total exactly at the inch mark.

2014

One day after a sultry high of 86° (which drove me to turn on my AC for the first time this year), today was overcast, with afternoon temperatures only in the upper 50s.

2021

Morning sunshine gave way to overcast skies in the afternoon, and rain moved in after 4:00 (just as the Memorial Day weekend was getting underway).  The rain became steady and wind-swept for the rest of the day (peak gust was 36 mph at Central Park), and amounted to 1.22", which was a record amount for the date (the rain continued thru the morning of 5/29).  The temperature dropped from 69° in the early afternoon to 49° less than twelve hours later.  This was the latest date for a reading in the 40s since 2000 (when it happened on 6/7). 

 

 

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