Summer of 2015 Highlighted by Record Streak of Days Above 80 Degrees
A Trend Towards Fewer Cool Summer Nights (Lows in 50s)

September 2015 Weather Recap: New York's Warmest on Record

Trophy.winnerAfter experiencing near record-warmth in May (second warmest) and August (third warmest), 2015 can now lay claim to the warmest September on record, easily topping 1961's previous record by 0.9 degrees.  Like much of the summer, September's average temperature was greatly influenced by the lack of any incursions of chilly air masses.  The coolest reading was 56°, which matched Sept. 1921 for the mildest minimum reading for the month.  (September's coolest reading is typically around 49.)  And only five days had lows in the 50s, which was well below the average of 13.  Finally, the month joined Sept. 1968 and 1921 as the only Septembers to have no high temperatures cooler than 70 degrees.  A typical September sees five or six such days.  Other interesting facts:

 

  • Nine days had mean temperatures (average of the high/low) that were 10 degrees or more above average, but that was no match for the 14 such days in Sept. 1961.  (1961's average high was just 0.1 degree lower than 2015, but 2015's average low was 1.7 degrees milder.)
  • This September matched that of 2005 by having just one day with a below average mean temperature.  However, in 2015 that day was just one degree below average while 2005's was four degrees below the norm.  (And Aug. 2015 had only a handful of days that were below average, and they were all also just one degree below average.)
  • This was the first time since 1998 that September was warmer than June, which was close to average (74.4 vs 71.2).
  • Despite this year's record warmth, Sept. 1961 had more 90-degree days (8 vs. 6) while Sept. 2005 had more 80-degree days (23 vs. 19).
  • The hottest high temperature of the year occurred on 9/8 when the mercury reached a record 97 degrees.  (However, the year's highest mean temperature occurred on 7/20, with a high of 94/82).

 

Highline

 

  • The month saw the end of the longest streak of 80-degree days on record, 62 days.  Then shortly thereafter another warm temperature record was established - most total days  of 80-degree+ in a year (which grew to 114 days by the end of the month).  In both instances the previous record holder was 1944.  (Despite this record number of 80-degree days, 2015 ranks 12th for most lows of 70 or warmer.)
  • The month was on the dry side and featured a 15-day stretch with no rain (the second longest streak of the year).  In total 3.28" of rain fell, with most of it falling on two days - a record 1.51" on 9/14 and 1.27" on 9/30.  And although the month had below average rainfall (one inch below average), it had considerably more rain than any of the next eight warmest Septembers, which averaged just 1.58".

 

10 WARMEST SEPTEMBERS 
(Since 1900)
           
  Mean Average Max Min
 Year Temp High Low Temp Temp
2015 74.4 82.6 66.3 97 56
1961 73.5 82.5 64.6 95 49
2005 73.3 81.6 65.0 92 50
1959 72.3 80.9 63.6 93 46
1931 72.3 81.3 63.3 99 49
1921 72.1 80.7 63.5 96 56
1930 72.0 79.8 64.1 88 52
1983 71.8 80.5 63.0 99 49
1971 71.5 77.3 65.8 91 49
2010 71.1 78.7 63.4 96 54
           
Source: NOAA Local Climatological Data

 

 

 

 

 

 

 

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Ken K. in NJ

Thanks for this rob, totally fascinating data.

Pretty amazing run of weather even into he past few days. I think we set a household record by putting the central A/C on again early on 9/30 (turning it off yesterday morning, 10/1), followed today by putting the heat on for the first time.

I'm now wondering about whether we got near a record for the most consecutive days of 70 degrees or higher, which I guess just ended yesterday.

Thanks again.

--Ken

Rob

If the temperatures we had on 10/1 and 10/2 had occurred during the last two days of September, Sept. 1961 would still be the warmest. Yes that was quite a streak of 70+ days (118), probably a record but, believe it or not, I haven't investigated it!

Biebs

The 70+ streak tied a record, but didn't break it. Suprisingly, the 70+ streak is from 1994 (5/28 - 9/21) which wasn't a particularly warm summer.

Rob

Thanks for investigating. However, the date range of 1994's streak is 117 days while this year's was one day longer (6/5 - 9/30).

Rob

William

the fifteen day streak with no rain this month was the longest rain free streak in September since 1959 when there was one of sixteen days.

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