Showers and thunderstorms developed across Long Island and portions of New York City during the early morning hours in association with a surface trough south of the area. With weak steering flow and high moisture content (precipitable water values 2+ on the Upton, NY sounding), this resulted in flash flooding across portions of Nassau and Suffolk Counties. While rainfall totals averaged 1-2 inches across New York City and Long Island, portions of southern Nassau County and southwestern Suffolk County received 3-5 inches of rain. Reports from automated weather observing stations include 3.34 in West Babylon, 3.39 in Freeport, 4.25 in West Gilgo Beach, and 4.46 in Merrick. CoCoRaHS observers reported 3.69 one mile NNE of Wantagh, 4.05 ENE of Copiague, and 5.41 one mile SSW of Massapequa.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 06:20:00 to 10-SEP-20 07:00:00 (EST-5)
Location: WANTAGH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Social Media

Park Avenue was closed at Oakland Avenue in Wantagh due to flooding.

Flash Flood in SUFFOLK, NEW YORK
From 10-SEP-20 07:00:00 to 10-SEP-20 07:40:00 (EST-5)
Location: BABYLON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Eaton Lane and Sequams Lane Center in West Islip were closed for approximately three hours due to flooding.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 06:20:00 to 10-SEP-20 07:00:00 (EST-5)
Location: SEAFORD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Several roads were reported flooded in Seaford including Jackson Avenue near the intersection with Fulton Avenue and the intersection of Washington Avenue and Sunrise Highway.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 05:54:00 to 10-SEP-20 07:00:00 (EST-5)
Location: WANTAGH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

All lanes were closed in both directions at Exit 5 on the Wantagh State Parkway in Wantagh due to flooding.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 06:50:00 to 10-SEP-20 07:00:00 (EST-5)
Location: ARLYN OAKS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Water rescues were reported on Merrick Road at Arlyn Drive W. in Massapequa. In addition, the intersections of Sunrise Highway and E. Walnut Street and Sunrise Highway and Hicksville Road were closed due to flooding.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 05:50:00 to 10-SEP-20 07:00:00 (EST-5)
Location: LIDO BEACH
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Numerous roads were reported flooded in Lido Beach including Blackheath Road at Richmond Road, Fairway Road at Eva Drive, and Lido Boulevard at Regent Drive.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 08:00:00 to 10-SEP-20 08:30:00 (EST-5)
Location: NASSAU SHRS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Numerous water rescues were reported and several cars were stranded on Sunrise Highway in Massapequa due to flooding near the LIRR underpass and Sunrise Mall. In addition, Massapequa Avenue was closed in front of Fairfield Elementary School due to flooding.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 05:50:00 to 10-SEP-20 07:00:00 (EST-5)
Location: BARNUM IS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Numerous roads were flooded in Long Beach, including East Broadway near Franklin Boulevard and Long Beach Boulevard at the McDonalds. The first day of school was postponed as buses could not navigate roads as they became impassable.

Flash Flood in SUFFOLK, NEW YORK
From 10-SEP-20 07:10:00 to 10-SEP-20 07:40:00 (EST-5)
Location: BABYLON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Several cars were stranded in high water on Great East Neck Road at Flurry Lane in West Babylon.

Flash Flood in SUFFOLK, NEW YORK
From 10-SEP-20 07:02:00 to 10-SEP-20 07:40:00 (EST-5)
Location: AMITYVILLE ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

The exit ramp for Exit 35 (Wellwood Avenue) on the Southern State Parkway in North Lindenhurst was closed due to flooding.

Flash Flood in NASSAU, NEW YORK
From 10-SEP-20 05:17:00 to 10-SEP-20 07:00:00 (EST-5)
Location: MERRICK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Extensive street and highway flooding was reported in Merrick. Numerous intersections were reported flooded along Merrick Road, including Kenny Avenue, Fox Boulevard, and Henry Street, although no vehicles were stranded and no water rescues were needed. In addition, the parking lots of numerous stores and strip malls were inundated along Merrick Road between the Meadowbrook State Parkway and the Wantagh State Parkway and remained inaccessible through at least 11:00am. Additional flooding was reported at the intersections of Lindenmere Drive and Hedge Lane, Cheryl Road and Judith Drive, and Beach Drive and Florence Street.

Flash Flood in SUFFOLK, NEW YORK
From 10-SEP-20 07:10:00 to 10-SEP-20 07:40:00 (EST-5)
Location: AMITYVILLE ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Vehicles were reported stuck in flood waters at the intersections of Wellwood Avenue and 7th Street as well as South Delaware Avenue and East Hoffman Avenue in Lindenhurst as well as along the Sunrise Highway service road in Copiague and Amityville and along Great Neck Road in Copiague.