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New York's Lengthiest & Hottest Heat Waves
Ten Inches of Monthly Precipitation Becoming More Common in New York

Very Warm Low Temperatures Made July 2013 Heat Wave New York's Hottest on Record

Veryhot

 

In a recent post about New York's major heat waves, a key finding was that the nine-day heat wave of July 1977 had the distinction of being the hottest heat wave of seven days or longer.  This was based on the average high temperature.  However, when low temperatures are added to the equation a different story emerged. 

 

It turns out that New York's seven-day heat wave of July 14-20, 2013 had the warmest average low of any lengthy heat wave - 79.0°.  And although the average high during these days, 94.6°, put it in the middle of the pack, when it was averaged with the low temperature, the resulting mean temperature of 86.8° (the average of the high and low) made it the hottest of all the major heat waves.  It bested a heat wave in August 1988 by 0.1 degree.  And 1977?  It fell to third.

 

Heatwave5

 

12 HOTTEST HEAT WAVES RANKED BY MEAN TEMPERATURE  
(Heat Waves of 7 Days or More)  
           
    Average Average    
Year Dates (# of Days) High Low Mean  
2013 July 14-20 (7) 94.6 79.0 86.8  
1988 Aug 9-15 (7) 95.3 78.0 86.7  
1977 July 13-21 (9) 97.1 75.6 86.4  
1955 Aug 1-7 (7) 96.1 75.3 85.7  
1944 Aug 10-17 (8) 96.6 74.0 85.3  
1973 Aug 28 - Sept 4 (8) 95.4 75.0 85.2  
1993 July 7-16 (10) 95.7 74.5 85.1  
1983 July 12-18 (7) 95.0 74.9 85.0  
2002 July 29 - Aug 5 (8) 94.0 75.5 84.8  
2002 Aug 11-19 (9) 94.2 75.2 84.7  
1953 Aug 24 - Sept 4 (12)* 95.4 73.9 84.7  
1991 July 15-21 (7) 96.6 71.7 84.2  
           
*Lengthiest on record        

 

Another striking characteristic of July 2013's heat wave was its relatively small diurnal variation - average high and low were 15.6 degrees apart.  By comparison, most of the other heat waves among the twelve hottest had diurnal variations greater than twenty degrees.  (1991's was the greatest, at nearly 25 degrees.)  Meanwhile, the last two days of 2013's heat wave had diurnal variations of just 13 degree and 12 degrees (high/low of 96°/83° and 93°/81°).

 

Comments

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Arthur  M.

The urban heat island (UHI) effect appears to have contributed to the July 14-20, 2013 period morning low temperatures that barely reached the upper 70's. Your climate stats are great and very useful. Your data clearly shows that if you consider the surface peak temperatures by decade that at least in the case of NYC there is no upward trend in surface temperatures as claimed by the climate alarmist community. In fact NYC is probably trending slightly downward with regard to 90 plus temperatures and when you consider the UHI effect which over the decades should contribute to an increase in surface temperatures as we build more and more buildings and add more AC units (heat sources) in the city, these high and low temperature statistics are amazing. Which in it self implies that natural climate variability is significantly greater than human derived or caused contributions. I often wonder how did the several mile thick glaciers that were covering most of northern North-America melt and retreat to the far reaches of Canada. Natural variability is king. I always enjoy visiting your web site and reviewing your weather stats!

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