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90-Degree Days in September
Summer of 2015 Highlighted by Record Streak of Days Above 80 Degrees

Recap of August 2015: New York's Third Hottest on Record

Hot.august

 

Just three months after an exceptionally warm May, which was New York's second warmest on record, August 2015 crossed the finish line as third warmest.  Although the number of 90-degree days, eight, was double the average, what really contributed to the month being so warm was the absence of any outbreaks of Canadian air masses.  Every day had a high of 80° or warmer - a first for August (a typical August sees seven days with highs cooler than 80°.)  Only four days had below-average mean temperatures; the most below average was just -1.5 degrees on two days.  Below are a number of other noteworthy findings:  

   

  • An extended streak of 80-degree days that began on July 10 continued through August.  By 8/31 it had grown to 53 days, making it the second longest such streak - and it was expected to eclipse 1944's all-time streak of 59 days (it did). 
  • The month was also characterized by plentiful sunshine, with 23 days that were either sunny or clear.  Cloud cover is measured on a scale of 0 to 10, with 0 being clear and 10 overcast.  August averaged a cloud cover rating of 2.1, making it the sunniest month of the past five years (this information is reported sporadically in prior years).  This included sunny/clear sky conditions for the first nine days of the month as well as the final six days.
  • Four years ago August 2011 became the wettest month on record, with 18.95" of rain measured.  Since then the four Augusts that followed have all had less than three inches of rain.  This August measured 2.35", about half the typical amount.  Half of the month's rain poured down during the morning of 8/11.
  • July (2.3 degrees above average) and August (3.8 degrees above average) rank as the fifth warmest July/August combo on record (tied with 1995).  What makes 2015 stand out is that there were a lot less 90-degree days than the other July/August combos ranked in the top 10. 

 

FIVE HOTTEST AUGUSTS
               
  Average   Hottest Days of  
  High Low Mean Temp 90+ 80+ Rain
1980 88.3 72.2 80.3 97 15 28 1.16"
2005 87.1 72.2 79.7 99 9 28 3.96"
2015 86.9 71.0 79.0 95 8 31 2.35"
1988 87.0 70.5 78.8 99 10 26 2.19"
2001 86.5 70.8 78.7 103 8 28 2.56"

 

HOTTEST JULY/AUG COMBOS
         
  Mean Temp Days of
  July Aug July/Aug 90+
1980 79.3 80.3 79.8 26
1955 80.9 78.1 79.5 24
2010 81.3 77.4 79.4 28
1988 79.3 78.8 79.1 23
2015 78.8 79.0 78.9 13
1995 79.2 78.6 78.9 24
1993 80.2 77.2 78.7 30
2005 77.5 79.7 78.6 17
1983 79.5 77.7 78.6 23
1944 79.4 77.8 78.6 28
         

 Sweaty

 

 

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Eugene

Hi Rob,
I must say that I'm amazed. First, that it was the 3rd warmest August on record, and second, it is the only August to have every day 80+. I'm also surprised about the July/August combo data. Is it me, or did this not seem like the 3rd warmest August or the 5th warmest July/August? It never seemed all that hot to me. It could be that there was only one official heat wave (August 15-18) and only 13 days of 90+ between both July and August. I see from your charts that July/August 2015 was really quite unusual compared to the other years. Very different from the normal hottest summers. Actually I love when these kind of unusual weather scenarios occur...it keeps things very interesting.

Rob

Thanks Eugene, I agree with you 100% and that's what I've been saying to friends. It didn't feel that bad. I thought perhaps it was because I'm back to working full-time in an air-conditioned office, plus casual clothes are the norm in the office. I guess it was because there were no triple-digit days, not a whole lot of 90-degree days and those we have were largely 90-92. And like you said there was only one heat wave, and that was just four days. Also, 4th of July was on the cool side.

Winter, however, now that felt cold. My lasting impression of 2015 is walking past the frozen fountain at Bryant Park every day coming from work.

Besides our streak of 80-degree days, another record we may threaten is total number of 80-degree days in a year. The record is 108 days in 1944 (not surprisingly, the same year as the 59-day streak of 80-degree days). Through today (Sept. 3) we've had 99 days so we have a good shot.

Thanks again for your message.

Rob

Biebs

I've been following this data locally and was considering sending a note this AM about the September record (A full 1 degree warmer seems quite significant, but the gap between 1 and 2 in January (1932 was 1.7 degrees warmer than 1950) and April (2010 was 1.1 degrees warmer than 1941) are higher gaps between 1 and 2.
What I find really interesting about this year is that 2015 overall (through September) is a slightly above average year in weather (Actually slightly below trailing 10 and trailing 30 year averages); but the year is broken up into 2 distinct sections.

Jan - Mar is the coldest Jan-Mar since 1940 (And the coldest against 10/30 year trailing average in NYC history)
Apr - Sep is the 2nd warmest Apr - Sep in history (only 2010 was warmer). I haven't looked through the data, but I imagine this year has the highest variance of weather against the average from month to month

Rob

Yep, this has been quite a year for contrasts in seasons. Perhaps you know if there have been other years that have had so many months rank so high for temperature extremes? You mention April-Sept being second warmest - do you know if May-Sept also ranks second? Despite how warm it's been for the past five months I still can't shake the image of the frozen fountain at Battery Park from my memory - or ice still surrounding Manhattan at the end of February!

Biebs

Clearly this comment was meant to go in September.

For 2015, the rankings are as followed:

Apr - Sep: 2nd - 71.1 (2010: 71.3)
May - Sep: 1st - 74.4 (2nd 2010: 74.0)
Jun - Sep: 3rd - 75.9 (1stT 2005/2010: 76.2)
Jul - Sep: 1st - 77.4 (2nd 2005: 76.9)
Aug - Sep: 1st - 76.8 (2nd 2005: 76.5)

Jan - Feb: Coldest since 1920
Jan - Mar: Coldest since 1940

Only Feb Ranked in bottom 10 for cold (#1 by a large margin for difference against 30 year average)

William

how did July 1944 have a hotter average mean temperature than August 2015? there are a handful of observations that contradict this fact. August 2015's hottest & coldest readings were 95 & 63 while July 1944's were 94 and 61. the "chilliest" high temperature was 81 in August 2015 while in July 1944 the chilliest was 80. there were (19) 70° nights in 08/2015 and there were 16 70° nights in 07/1944. the warmest low in 08/2015 was 78° and the warmest low in 07/1944 was 76°.

Rob

However, July 1944 had sixteen days in the 90s while August 2015 had half that number. And while the average low of August 2015 was 1.5 degrees warmer than July 1944 (71.0 vs. 69.5), July 1944's average high was 2.3 degrees hotter (89.2 vs. 86.9).

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