Persistently Extreme: September 2011 Summary

Dr. David A. Robinson
New Jersey State Climatologist
Center for Environmental Prediction, School of Environmental and Biological Sciences/NJAES, Rutgers University
October 4, 2011

The beat goes on. September brought much of New Jersey a very wet month; this on the heels of record-shattering August rainfall. So too were temperatures well above normal; thus continuing an almost unbroken string of warmer-than-average months extending back to spring 2010. With three months remaining in 2011, the Garden State is knocking on the door of both the wettest (1996) and warmest (1998) years on record since statewide averages began to be compiled in 1895. Neither may be achieved, however to be simultaneously challenging both is quite remarkable.


September precipitation averaged 7.00". This is 2.93" above the 1981-2010 average and ranks as the 10th wettest on record (Table 1).

Rank Year Sept. Prcp
1 1938 9.78"
2 1999 9.58"
3 1934 8.61"
4 1975 8.16"
5 1944 8.14"
6 1907 8.12"
7 1966 7.82"
8 1960 7.73"
9 1989 7.31"
10 2011 7.00"
11 1935 6.60"
12 2008 6.27"
13 2003 6.17"
14 1979 6.13"
15 1899 5.91"

Table 1. The fifteen wettest Septembers across NJ since 1895.

August and September combined totaled 23.89". This is the largest consecutive two-month total of any pair of months. The July-August 2011 pair is second wettest at 20.99". Far behind in third place is March-April 1983 at 16.63". This is yet another example of how extraordinarily wet this past August was compared to any month in the past 117 years!

Precipitation for the first nine months of 2011 totals 52.71". This is a record for any January-September and means that with average precipitation from October-December (11.47"), 2011 will be the wettest calendar year on record (the current record is 59.98" in 1996). The past twelve months have seen an average of 63.38" fall across the state, ranking 3rd greatest of any twelve-month interval on record (Table 2). When considering just the northern portion of the state (Hunterdon, Somerset, Union counties and north), the 73.87" over the past twelve months easily surpasses any other twelve-month period on record (the next highest is 67.24" during the twelve-month interval ending in July 1984). Budd Lake (Morris) received 74.08" during the first nine months of 2011. The state record for a calendar year is 85.99" at Paterson (Passaic) in 1882. Other NJ stations may challenge either the state record or individual station records. Stay tuned to see what these coming months may bring.

Rank Month Range End Year 12-month Total
1 Apr-Mar 2010 66.60"
2 May-Apr 2010 64.36"
3 Oct-Sep 2011 63.38"
4 Jun-May 2010 63.28"
5 May-Apr 1939 61.38"
6 Oct-Sep 1952 61.23"
7 Dec-Nov 1975 61.21"
8 May-Apr 1973 61.11"
9 Jun-Jul 1972 60.99"
10 Aug-Jul 1984 60.63"

Table 2. The ten wettest twelve-month intervals across NJ since 1895.

Returning back to this past September, the wettest portion of NJ was in the northwest where the Mt. Olive (Morris County) CoCoRaHS station saw the most rain, an impressive 16.88". With just a few drops less, Blairstown (Warren) received 16.87", with Oxford Township (Warren) coming in with 16.28". Six other locations in this region had between 15.00"-15.99" and fifteen stations had 14.00"-14.99". Unlike this past August, there was an area of the state with sub-average precipitation. Sea Isle City (Cape May) only saw 1.54" fall, with the Cape May County communities of Stone Harbor (1.72") and Middle Township (1.76") not much wetter. It should be noted that none of these totals include rain that fell after approximately 7AM on the 30th (CoCoRaHS observation time) as those totals will be included with rain falling before 7AM on October 1 as part of October's totals.

The three wettest stations above also lead the way with remarkable August-September totals that include 34.43" in Mt. Olive, 34.31" in Blairstown, and 32.59" at Oxford. Some stations in Sussex, Passaic, and Hunterdon counties also had at least 30.00". Another nine counties had stations receive between 24.00"-29.99" (Bergen, Union, Middlesex, Somerset, Mercer, Monmouth, Gloucester, Salem, and Cumberland). That is fourteen of NJ's 21 counties.

Only eight September days failed to see measurable rain fall at one or more NJ stations (1st-4th, 13th, 18th, 19th and 26th). The first and largest event of the month was associated with a moist tropical feed of moisture that included the remnants of Tropical Storm Lee. Between the 5th and 8th, centered on a very wet 6th, as much as 9.48" fell in Blairstown, 9.45" in Liberty Township (Warren), and 9.18" in Oxford Township. Of 190 CoCoRaHS stations reporting on these days, seventeen recorded 8.00"-8.99", 21 from 7.00"-7.99", 22 between 6.00"-6.99", and 31 from 5.00"-5.99". Heavy rain fell in most regions of the state except for the southeast, where Middle Township and Upper Township in Cape May County received 0.13" and 0.15" respectively (Figure 1). Moderate to major flooding was renewed within the Passaic and Raritan basins. Though not as severe as just days earlier, the combination of heavy rain, saturated soils and rivers still running high closed a number of roads and once again flooded homes and businesses in a number of locations. This flooding event was worse along the Delaware than earlier Irene flooding. A mudslide occurred by Mountain Lake in Liberty Township (Warren), damaging several homes. There was no wind damage associated with this event.

On the 10th a localized thunderstorm dropped 2.16" in Oswego Lake (Burlington) and 2.13" in Tabernacle (Burlington). The 11th brought thunderstorms to Gloucester, southern Burlington, and southern Ocean counties, with 1.86" in Stafford Township (Ocean), 1.56" at Medford Lakes (Burlington), and 1.17" in Little Egg Harbor (Ocean). Hail was observed and some trees and poles blew down in Springfield (Burlington). Localized thunderstorms on the 14th brought hail to Sussex County but light rain totals. A quickly developing, isolated thunderstorm over Atlantic City (Atlantic) on the 15th tragically resulted in the lightning death of a construction worker.

Only scattered light rainfall occurred over the next week, a welcome period for some drying out. A statewide soaking arrived on the 23rd. Northwestern areas caught the most, with 2.78" in Jefferson Township (Morris), 2.58" in Lebanon (Hunterdon), and 2.52" at Denville (Morris) leading the way. Of 167 stations reporting, eleven saw 2.00"-2.50" and 101 between 1.00"-1.99". The pattern of rainfall distribution was similar to the early-month event, with southeast areas receiving 0.50" or more this time.

Adding insult to injury, the northwest corner of the state was clobbered with more heavy rain in the early morning of the 28th. Mount Olive (Morris) received 4.99", three Blairstown (Warren) stations saw 4.91", 4.65" and 4.43", Liberty Township (Warren) 4.78", Hackettstown (Warren) 4.77", and Allamuchy Township (Warren) 4.47". Twenty other stations in the Hunterdon, Warren, Sussex, and western Morris area received between 3.00" and 4.21". Of the 8450 CoCoRaHS stations reporting nationwide on the morning of the 28th, thirteen of the top twenty were from New Jersey! As a result, dangerous flash flooding occurred on numerous streams and rivers, particularly the South Branch of the Raritan River, where the gauge at Four Bridges went above flood stage for the 6th time since late August. Later that day a thunderstorm brought pea-size hail to Linwood (Atlantic).

Scattered heavy rain fell in thunderstorms on the 29th. Mt. Olive was again soaked with 1.93", Palisades Park (Bergen) saw 1.52", and New Brunswick (Middlesex) 1.45". There was minor wind damage in Warren County and numerous trees toppled by winds in Secaucus (Hudson) and Englewood Cliffs (Bergen). Coastal areas saw some moderate rain on the 30th, with 1.37" at West Creek (Ocean).

With all of the moisture in the air and on the ground, fog was reported at some locations in the state on seven days, including the 7th, 22nd, 23rd, and 25th-28th. It was most widespread on the 23rd, 26th, and 27th. The abundant moisture also resulted in swarms of mosquitoes irritating many NJ residents throughout the month.


The statewide average September temperature of 69.3° comes in as the 5th warmest. This is 3.4° above the 1981-2010 average. Five of the ten warmest Septembers of the past 117 years have occurred since 1998 (Table 3). September continues a persistent pattern of above-average temperatures across NJ. Going back to March 2010, sixteen of nineteen months have averaged above the 1981-2010 mean. Of those sixteen, a stunning ten months have ranked in the top ten for warmth, including the warmest April (2010) and July (2011) on record.

Rank Year Sept. Temp.
1 1961 71.4°
2 2005 71.0°
3 1931 70.1°
4 2010 69.5°
5 2011 69.3°
6 1998 68.9°
7 1959 68.8°
8 1945 68.7°
9 2002 68.4°
10 1970 68.3°

Table 3. The ten warmest Septembers across NJ since 1895.

September's warmth was more a function of nighttime minimum temperatures rather than daytime maximums. For instance, at New Brunswick (Middlesex) the average maximum was 1.5° above normal while the minimum was 6.5° above normal. This was due to frequent cloud cover and the overall moist atmospheric conditions throughout much of the month.

Based on daily observations from approximately 50 stations, ten September days had maximum temperatures between 85° and 88° at one or more stations. Hawthorne (Passaic) and New Brunswick reached 85° on the 1st. That mark was again achieved at Haworth (Bergen), Chatham (Morris), and Jersey City (Hudson) on the 3rd. New Brunswick and Hillsborough (Somerset) saw 87° maximums on the 4th. New Brunswick, Woodstown (Salem), and Oswego Lake (Burlington) reached 85° on the 5th. Sicklerville (Camden) hit 87° on the 7th, as did Oswego Lake, Hawthorne, and Mullica (Atlantic) on the 9th. Top warmth of 86° occurred at Bethel Mill Park (Gloucester) and Mullica on the 10th, and at South Harrison (Gloucester) on the 13th. The 14th was the warmest day of the month, with 88° reached at Piney Hollow (Gloucester), South Harrison, Bethel Mill Park, and Sicklerville. Eleven other stations reached 87° that day, with the coolest locations in the state at High Point Monument (Sussex) and Atlantic City Marina (Atlantic) with maximums of 78°. Woodbine (Cape May) reached 85° on the 15th.

With no 90° or higher maximums this month the last such day of 2011 was 8th of August. This is quite early, despite August being the 28th warmest on record and September the fifth warmest. Again, this is testimony to the cloudy, moist conditions during these months that put a check on daytime maximums along with the aforementioned elevated minimums. Still, the number of 90° or greater maximums was several days above average in 2011, though much lower than in the record setting 2010 summer. For instance, Newark Airport (Essex) and the Atlantic City Airport in Pomona (Atlantic) saw 31 such days this year compared to 54 and 46, respectively, in 2010. Other stations came in with the following number of days of 90° or above maximums this summer (with 2010 values in parentheses): Seabrook Farms (Cumberland) 29 (50), Hillsborough (Somerset) 29 (54), Trenton Airport (Mercer) 26 (52), New Brunswick (Middlesex) 24 (51), Sussex (Sussex) 8 (17), and Atlantic City Marina (Atlantic) 8 (10).

On the cool side of the ledger, low temperatures fell into the 30°s and 40°s on seven September mornings. The 15th saw Walpack (Sussex) reach 40° and three other stations 42°. The 16th was the coolest morning of the month, with Walpack at 37°, High Point Monument (Sussex) at 39°, and 25 stations between 40°-45°. West Cape May (Cape May) was mildest that morning at 53°. Five stations got down to 42° on the 17th, Pequest (Warren) was 38° and Basking Ridge 39° on the 18th, and Walpack 39° and Basking Ridge 41° on the 19th. In the Pine Barrens, Berkeley Township (Ocean) reached 46° and Oswego Lake (Burlington) 48° on the 20th. On the last day of the month, Berkeley Township, Basking Ridge, and Pequest fell to 48°.

Other Variables

Barometric pressure topped out at 30.45"-30.50" of mercury on the 17th. The lowest pressure of the month occurred on the 29th, with a number of stations recording values between 29.55"-29.60".

Aside from localized strong winds in several thunderstorms, September was not a windy month. Winds gusted to 41 mph at Harvey Cedars (Ocean) and Bivalve (Cumberland) on the 15th, when ten other stations had gusts in the 30-39 mph range. High Point Monument (Sussex) gusts reached 42 mph on the 16th. The most damaging winds were on the 29th, when Point Pleasant (Ocean) gusted to 56 mph, Atlantic City Marina (Atlantic) to 46 mph, Stewartsville (Warren) to 43 mph, and seven other stations gusted into the 30-39 mph range.

For those seeking more detailed information on hourly, daily and monthly conditions, please visit the following Office of the NJ State Climatologist's websites:

NJ Weather and Climate Network
NJ Community Collaborative Rain, Hail and Snow Network
NJ Snow Event Reports

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