A cluster of heavy thunderstorms produced torrential rain that resulted in widespread and significant flash flooding across the region.  Maximum 1 hour rainfall rates were estimated at 2 to 3 inches.  The storm total rainfall for this event ranged from around 3 to 6 inches.  Nassau Community College measured 5.18 inches.  Other amounts included 4.20 inches in Holtsville and 3.35 inches in Fresh Meadows.
Thunderstorms produced many frequent and intense lightning strikes that resulted in more than 20,000 customers without power across portions of Long Island, as reported by the Long Island Power Authority.
A severe thunderstorm produced an EF1 tornado in East Islip Terrace.

Thunderstorm Wind in SUFFOLK, NEW YORK
From 18-JUL-07 08:15:00 to 18-JUL-07 08:15:00 (EST-5)
Location: OAKDALE
Magnitude: 60.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A severe thunderstorm produced high winds that downed numerous trees in Oakdale.

Flash Flood in QUEENS, NEW YORK
From 18-JUL-07 06:45:00 to 18-JUL-07 06:58:00 (EST-5)
Location: FLUSHING
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding occurred along portions of the Long Island Expressway at Exit 18, Maurice Avenue and at Northern Blvd. on the Cross Island Parkway.

Flash Flood in KINGS, NEW YORK
From 18-JUL-07 07:05:00 to 18-JUL-07 07:20:00 (EST-5)
Location: CONEY IS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flash flooding occurred along portions of the Gowanus Expressway near I-278, Brooklyn Queens Expressway.

Flash Flood in SUFFOLK, NEW YORK
From 18-JUL-07 09:45:00 to 18-JUL-07 10:00:00 (EST-5)
Location: PATCHOGUE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Significant street flooding was reported.

Flash Flood in NASSAU, NEW YORK
From 18-JUL-07 07:19:00 to 18-JUL-07 07:41:00 (EST-5)
Location: ELMONT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flash flooding occurred along portions of the Northern State Parkway and Hempstead Turnpike in Elmont and on multiple streets in Port Washington, where road closures occurred.

Flash Flood in SUFFOLK, NEW YORK
From 18-JUL-07 07:50:00 to 18-JUL-07 08:05:00 (EST-5)
Location: HUNTINGTON
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flash flooding occurred along portions of Route 110 in Huntington.

Flash Flood in QUEENS, NEW YORK
From 18-JUL-07 08:58:00 to 18-JUL-07 10:03:00 (EST-5)
Location: LITTLE NECK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding resulted in a road closure at 188th Street along the Long Island Expressway.  The Long Island Railroad Station in Bayside was flooded.  The Cross Island Parkway flooded at the Throgs Neck Bridge.

Flash Flood in KINGS, NEW YORK
From 18-JUL-07 09:04:00 to 18-JUL-07 09:19:00 (EST-5)
Location: BENNETT FLD NAS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding was reported along the east bound portion of the Belt Parkway near the Mill Basin Draw Bridge.

Tornado in SUFFOLK, NEW YORK
From 18-JUL-07 08:25:00 to 18-JUL-07 08:30:00 (EST-5)
Location: ISLIP TERRACE
Tornado F-scale: EF1
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

National Weather Service Meteorologists investigated storm damage in the Islip Terrace area and confirmed that tornadic damage occurred.
The tornado touched down in the town of Islip Terrace near the intersection of Irish Lane and the north service road of Sunrise Highway.  It moved east to northeast across Carleton Avenue, Roslyn, and Nassau Streets, and lifted near Nassau and Kunigunda Place.  The path was discontinuous over two thirds of a mile.  The width was narrow at first, only around 50 yards near the intersection of Irish Lane and the north servicee road of Sunrise Higyway, then fanned out to 150 yards further east.
Most of the damage was to hard wood trees.  Twisted off branches were evident throughout the damage path.  Some trees were snapped off half way up, including some healthy 40 foot pines.
The Medical Arts Building at Irish Lane and Sunrise Highway sustained structural damage, with a significant loss of its' roof covering and the HVAC unit blown off its roof.  Other homes along the damage path also sustained minor damagee to siding and some directly from fallen trees.

Flash Flood in NEW YORK, NEW YORK
From 18-JUL-07 06:39:00 to 18-JUL-07 06:54:00 (EST-5)
Location: CENTRAL PARK
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding closed portions of the FDR Drive at 106th Street and 78th Street.

Flash Flood in NASSAU, NEW YORK
From 18-JUL-07 09:30:00 to 18-JUL-07 09:45:00 (EST-5)
Location: ROSLYN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Flash flooding caused closure of the Long Island Expressway at Exit 39.

Flash Flood in QUEENS, NEW YORK
From 18-JUL-07 07:09:00 to 18-JUL-07 07:24:00 (EST-5)
Location: BAYSIDE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Flash flooding of the Clearview Expressway occurred at 35th Avenue.