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September 2013

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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Extreme Weather: New York's Greatest One-Hour Rainfalls Since 1970

Torrential_rain2

 

I've written posts about New York's biggest rainstorms, its greatest daily rainfall totals and rainiest months.  This post adds to the genre by examining the City's most torrential one-hour rainfalls.  Although an inch of rain falling over the course of a day is a generous amount, a few times each year this amount pours down in just an hour - or less; occasionally the amounts exceed 1.50".

 

Although nor'easters and tropical systems are responsible for the greatest rainfall, these amounts are usually spread out over twelve hours or more.  Thunderstorms, on the other hand, are most likely to produce copious amounts of rain in short periods of time.  August has had the highest propensity for these torrential downpours.

 

60minutes

 

The greatest one-hour rainfall to occur in New York since 1970 was measured during the evening of Aug. 10, 2006 when 2.46" fell between 6:11-7:11 PM.  Five other huge 60-minute deluges have occurred around this date as well: 1.91" fell on Aug. 8, 2007; 1.40" fell on Aug. 9, 1976; 1.92" fell on Aug. 10, 1990, 2.09" fell on Aug. 12, 1989 and 1.76" fell on Aug. 12, 2020.  The most recent one-hour downpour of an inch or more occurred on July 8, 2021 when 1.56" fell between 5-6 PM.

 

Flooding_rain_central_park


(Like all of the previous analyses I've written about heavy precipitation, 1983 is a problem because it's rainfall totals were disavowed due to a malfunctioning rain gauge for most of the year.)

 

HIGH INTENSITY RAINFALL - 1 HOUR   
(1970 - 2013)      
       
Date Amount Time  
Aug 10, 2006 2.46" 6:11-7:11 PM  
July 17, 1995 2.09" 10:19-11:19 PM  
Aug 12, 1989 2.09" 12:45-1:45 PM  
Aug 10, 1990 1.92" 6:17-7:17 PM  
Aug 8, 2007 1.91" 4:36-5:36 AM  
July 29, 1980 1.78" 8:30-9:30 PM  
Sept 8, 2004 1.76" 6-7AM  
June 3, 1991 1.75" 9:06-10:06 PM  
.June 2, 2006 1.73" 2:35-3:35 PM  
Aug 14, 2005 1.73" 5:56-6:56 PM  
Aug 2, 1973 1.65" 8:30-9:30 AM  
Aug 16, 1993 1.58" 5:37-6:37 PM  
Oct 1, 2010 1.55" 4:05-5:05 AM  
July 6, 1975 1.43" 4-5PM  
Aug 9, 1976 1.40" 10-11PM  
June 22, 1973 1.40" 1-2PM  
June 6, 1989 1.35" 1:25-2:25 PM  
May 23, 2013 1.32" 2:25-3:25 PM  
Aug 14, 2011 1.30" 1:02-2:02 AM  
July 6, 2005 1.26" Midnight-1AM  
Oct 21, 1995 1.26" 10:45-11:45 AM  
Note: Excludes 1983      
   

 

 

Beginning in 1982, the most drenching rains by 5-minute, 10-minute, 15-minute, half hour, and 45-minute intervals was reported in the monthly Local Climatological Data report.  The greatest amount of rain to fall in five minute's time was 0.63" on Oct. 14, 2011 between 12:36 and 12:41 AM.  (That's an hourly rate of 7.56".)  And there have been three instances where more than an inch of rain fell in just 15 minutes.  Frustratingly, this information is reported on an inconsistent basis (i.e., since 2000 this information is unavailable for 39 months). 

 

Boots_puddle

 

HIGH INTENSITY RAINFALL - 5 MINUTES  
(1982 - 2013)      
       
Date Amount Time  
Oct 14, 2011 0.63" 12:36-12:41 AM  
June 2, 2006 0.54" 2:46-2:51 PM  
July 26, 2009 0.46" 5:23-5:28 PM  
Aug 3, 2007 0.46" 10:16-10:21 PM  
Sept 10, 1992 0.45" 11:15-11:20 PM  
       
15 MINUTES (1982 - 2013)    
       
Date Amount Time  
June 2, 2006 1.25" 2:39-2:54 PM  
Aug 3, 2007 1.06" 10:06-10:21 PM  
Aug 12, 1989 1.02" 12:56-1:11 PM  
Aug 19, 2011 0.94" 6:26-6:41 PM  
Sept 10, 1992 0.92" 11:06-11:21 PM  
       
30 MINUTES (1982 - 2013)    
       
Date Amount Time  
Aug 12, 1989 1.64" 12:53-1:23 PM  
June 2, 2006 1.51" 2:35-3:05 PM  
June 3, 1991 1.47" 9:22-9:52 PM  
Aug 10, 2006 1.33" 6:12-6:42 PM  
Aug 10, 1990 1.22" 6:46-7:16 PM  
       

 

 

 

 

 

 

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