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January 2021

Analysis of Back-to-Back Days With the Same High & Low Temperatures

The same

 

In the years I've spent poring over New York's daily weather data, I'd notice pairs of days with the same high and low.  This analysis is the product of my curiosity about how common such pairings are.  On average, two occur each year (2.3 to be exact).  The most has been ten, which happened in 1931 and 2010.  There have been ten years with five or more pairs, including 2020.  Twelve years have had none.  (Of course, if temperatures were reported to one decimal place, these type of days would be even rarer than they already are.)  Here are some more interesting findings:

 

  • There have been three streaks that had three consecutive days with identical highs/lows - in 1988 (Aug. 3-5, all with a high/low of 89°/76°); 1984 (May 5-7, highs/lows of 69°/53°), and 1879 (May 8-10, 69°/49°).  And during the summer of 2013, after a high/low of 83°/67° on July 30-31, there was another day with the same high/low two days later, on Aug. 2.
  • There have been 23 pairs that missed by one degree of having a third consecutive day with the same high/low.  The most recent occurrence was in December 2010, when 12/7 had a high/low of 36°/30° after a high/low of 35°/30° on 12/5 and 12/6.  And each of the streaks of three-days (mentioned above) narrowly missed being four-day streaks:
    • Aug. 3-5, 1988's streak missed being a four-day streak when the high/low on Aug. 6  was 89°/75° instead of 89°/76°.
    • May 5-7, 1984's streak of 69°/53° was followed on May 8 by a high/low of 69°/55°.
    • The day before 1879's streak of May 8-10, with highs/lows of 69°/49°, the high/low was 70°/50°.
  • There have been three back-to-back pairs of days: July 28-31, 2010 (89°/74° on 7/28-29 and 85°/66° on 7/30-31); March 3-6, 1952 (pairs of 36°/32° and 42°/31°); and Aug. 17-20, 1906 (pairs of 85°/71° and 87°/77°).  And there has been one instance of three consecutive pairs of days: Dec. 16-21, 1901 (26°/20° on Dec. 16-17; 28°/20° on Dec. 18-19; and 26°/19° on Dec. 20-21).  (March 1952's and August 1906's streaks narrowly missed having three consecutive pairs.)
  • Of the 12 years with no pair of days, only one occurred after 1956 - 2000.  The other years: 1956, 1954, 1943, 1934, 1930 1924, 1916, 1903, 1889, 1881 and 1869.
  • There have been two instances of back-to-back years having the same pair of dates with the same high/low.  It first occurred on July 27-28, in 1897 and 1898.  (The pair of highs/lows in 1897 was 67°/64°, and 80°/74° in 1898.)  The second time was in 2020 and 2021 on May 29-30 (highs and lows of these pair were 81°/67° and 51°/47°, respectively).  And there have been five instances of pairs of the same dates being two years apart, most recently in 2018, when it and 2016 each had a pair of days on Dec 23-24.
  • July 27-28 has had the same high/low in six years, the most of any pair of dates: 2007, 1988, 1939, 1910, 1898, and 1897.
  • May 18-19, 1932 and May 18-19, 2005 had the same pairs of highs/lows (70°/53°).
  • There have been four pairs of 85°/70° highs/lows, which is the most frequent of any pair  (occurring on July 4-5, 2017; May 27-28, 2015; June 25-26 2014; and June 27-28, 1994).
  • July and August are the months most likely to have seen pairs of days with the same high/low (48 and 51 occurrences,respectively); February and October are the months least likely to report a pair of these days (with just 12 each). 
  • Hottest pair: 100°/79° on July 9-10, 1937; Coldest pair: 23°/14° on Jan. 28-29, 1986.

 Chart - back to back days_same high low

 

 


Review of 2020's Weather - New York's Second Warmest Year

Looking back

 

2020 was 2.4 degrees above average and became New York's second mildest year, behind 2012.  Only two months during the year, April and May, were chillier than average.  November became the mildest on record, July the seventh hottest, and February and March each became the eighth mildest.  January finished just outside the top 10, ranking eleventh, and June made it to sixteenth.  The summer was the fifth hottest (tied with 1983).  Despite 2020's warmer than average theme, there were some moments of chilliness worth noting:

 

  • April had no highs in the 70s or 80s for the first time in 80 years.
  • For the first time since 1978, May had readings in the 30s, and the low of 34° on the 8th was the coldest reading in May since 1891.
  • The year's last reading of 80° or warmer was on Sept. 10, which was the earliest of any year with 20 or more days with highs of 90°+.  A typical 90s/100s season lasts about three months (late May through late August), but in 2020 it was two months long (late June through late August).  However, the number of days in the 90s in 2020 was slightly more than average (20 days).
  • Later in September, the low of 49° on Sept. 21 was the the earliest for a low in the 40s since 1993.
  • Halloween had its first low of 32° or colder since 1988.

 

 Chart - 5 warmest years thru 2020

 

Chart - monthly temperature departure 2020

 

OTHER HIGHLIGHTS

  • The first half of the year was dry as the 16.15" measured was eight inches below average (the seventeenth driest first half on record).  The second half, however, had nearly twice as much precipitation, with 29.20" measured (three-and-a-half inches above average).  May and June both had less than two inches of rain, the first time since 1993 that these  months were this dry.  Overall, 2020 had 45.35" of precipitation, 4.59" below average.
  • Jan. 10 and 11 had record highs of 69° and 68°, respectively.  Meanwhile, chilly April's warmest reading was 68°, the first time since 1940 that April's mildest reading wasn't 70° or warmer.
  • The winter of 2020's last measurable snowfall was on Jan. 18, the earliest date on record for a last snowfall (breaking 2002's record by one day).  At the end of the year December's snowstorm produced more than twice as much as the previous winter.
  • Four tropical systems moved through the area.  The year's biggest rainmaker was from the first, tropical storm Fay, on July 10, which produced 2.54" of rain, most of it falling in a three-hour period during the afternoon.  While Fay brought the rain, tropical storm Isaias on Aug. 4 delivered ferocious winds, with 65-75 mph gusts common outside of Central Park (which had a peak gust of 48 mph).
  • July's coolest reading of 67° was the mildest coolest reading of any July.  Furthermore, July 2020 had the most lows in the 70s or warmer of any month (26).  This helped July become just the seventh to have an average temperature of 80° or above.
  • November had its first streak of six days with highs in the 70s (Nov. 6-11).  Later in the month, Thanksgiving Day's high of 65° tied for third warmest, and its low of 55° was mildest ever on this holiday.  The 0.79" of rain in the morning was the seventh greatest amount for Thanksgiving.
  • The 10.5" snowstorm of Dec. 16-17 was the biggest December snowfall in 10 years and the 13th during the month of 10 inches or more.  And at 1.7 degrees above average, December 2020 was the second mildest to have more than ten inches of snow.
  • An intense storm system on Christmas Day morning dumped the third greatest amount of precipitation on the holiday (0.92").  The day's high of 61° was the eighth reading in the 60s on the holiday.  The temperature dropped 32 degrees by midnight, which was the biggest daily drop in temperature all year.  2020 became just the second year (2015 is the other) to have highs in the 60s on Christmas Day (61°), Thanksgiving Day (65°) and Easter Sunday (63°).
  • Finally, the temperature profiles of 2020's first and last month were nearly identical.  However, December had more than twice the amount of precipitation than January and nearly five times as much snowfall.  Despite their similar temperatures January's was much more above average.

 Chart - jan v dec 2020

Other annual recaps:

2019

2018

2017

2016

2015

2014

2013

 

 

 

 


December 2020 Weather Recap: Two Storms Grab Headlines

Janice huff wnbc dec2020

 

The lasting memory of December 2020 will no doubt be the snowstorm of Dec. 16-17.  The 10.5" of snow that piled up was the biggest snowfall in December since 2010 and the thirteenth December snowfall of 10"+.  Another highlight was the intense rainstorm that blew through the City on Christmas morning.  The month was 1.7 degrees above average - the City's 34th mildest December (since 1869).  But despite being milder than average it had more days with highs of 32° or colder than all of last winter (four vs. three).  Additionally, the big snowstorm produced more than twice as much snow as the previous winter (10.5" vs. 4.8").

 

  • Five days had highs of 55° or milder while six days had lows of 25° or colder.  There were three days with highs in the low 60s, evenly spaced, on 12/1 (62°), 12/13 (62°) and 12/25 (61°).  Five of the six days with lows of 25° or colder had lows of 24° (the outlier was the reading of 20° on 12/19).
  • The mildest and coldest periods of December occurred during the fifteen-day period from Dec. 11 thru Dec. 25.

 

Chart - december 2020 coldest_mildest periods

 

  • Christmas Day's high of 61° (before sunrise) made it the eighth Christmas with a high in the 60s, and the 0.92" of rain that fell was the third greatest amount on the holiday.  After the high was reached the temperature fell steadily throughout the day and was down to 29° by midnight.  This 32-degree drop was the greatest of any calendar date in 2020.
  • Although the month was on the mild side, five Decembers in the past ten years were even milder.

 

Chart - mildest decembers since 2011

 

  • December 2020 was the 29th December with ten or more inches of snow (nearly 20% of all Decembers).  However, it was the second mildest December (after Dec. 1912) to have this much snow.  Although their average temperatures weren't quite as mild as this December, the Decembers of 1948, 1959 and 2003 had considerably more snow (25.3", 15.8" and 19.8", respectively).

 

Chart - snowy mild decembers

 

  • Much of the month's 4.61" of precipitation (0.61" above average) fell from three storm systems, all which produced more than an inch of precipitation:  1.13" on Dec. 4-5; 1.52" on Dec. 16-17; and 1.16" on Dec. 24-25.
  • Finally, similar to November, December had a lot of days with gusty winds, with Central Park having nine days with a peak gust of 33 mph or more.  The peak gust of 47 mph occurred early Christmas morning.

 

Chart - December peak wind gusts

 Snowstorm of dec 1617 2020

 

Other December recaps:

2019

2018

2017

2016

2015