The combination of an upper level disturbance crossing the southern Great Plains, upper level wind and a low level low pressure system moving east from Nuevo Leon, Mexico, and prior boundaries from earlier thunderstorms north of the Rio Grande Valley and from morning thunderstorms along the coast combined with deep atmospheric tropical moisture to create a thunderstorm system, including a heavy-precipitation supercell event. Measured and estimated rainfall of 4 to 8 inches in just two hours or so was too much for many drainage systems to handle, and significant flash flooding occurred during the peak of the October 1st (Friday afternoon) late afternoon and evening commute.  The peak of the heavy rainfall occurred between 330 and 7 PM, with some locations in east and northeast Brownsville receiving 7 to 8 inches in two hours or so within that window. Multiple records for daily rainfall were shattered, specifically in the Harlingen and Brownsville areas. Other reports of relatively minor flooding were received from neighboring Willacy and Hidalgo Counties. In addition to widespread flooding, some minor wind damage occurred along with a reported funnel cloud near Harlingen.
Total rainfall in east Brownsville for the date (October 1) ranged from 8 to nearly 11 inches.

Flood in CAMERON, TEXAS
From 01-OCT-21 20:30:00 to 02-OCT-21 08:30:00 (CST-6)
Location: PORT BROWNSVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Many portions of FM 802/Ruben Torres Blvd in Brownsville remained under several feet of water through the morning hours on the 2nd due to overwhelmed drainage systems in the area. It was not until around 9:00-9:30 AM local time on October 2nd that flood waters finally began to recede to the point of roads being traversable by mid-size cars.  Other high water of 2 to 3 feet along the sides of roads in a subdivision along Dana Avenue north of Ruben Torres Blvd. continued through the afternoon of October 2nd.  Damage to vehicles and property was not known as of this writing.

Flood in CAMERON, TEXAS
From 01-OCT-21 21:30:00 to 02-OCT-21 18:00:00 (CST-6)
Location: (BRO)BROWNSVILLE ARP
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A resaca continued to overflow its banks along Vermillion Avenue, from 1 to 1.5 miles north of the intersection with Boca Chica Blvd. (State Road 4), well into October 2nd with the road remaining closed. At 18 inches to two feet of water covered the center of the road, with up to four feet on the normal road edges. A CoCoRaHS observer along Vermillion Avenue reported more than 10 inches on the 1st, with most falling during this period; the two-day total was 13.53 inches. End time of the significant flooding is estimated.

Flash Flood in CAMERON, TEXAS
From 01-OCT-21 17:00:00 to 01-OCT-21 20:00:00 (CST-6)
Location: BROWNSVILLE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Brownsville Police Dept reported road closures due to flooding on East Washington St in downtown Brownsville.

Flash Flood in CAMERON, TEXAS
From 01-OCT-21 16:15:00 to 01-OCT-21 19:15:00 (CST-6)
Location: PORTWAY ACRES
Flood cause: Heavy Rain
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

A video was received from the public of water entering a home near the intersection of Jamie Zapata Ave and Robindale Blvd in Brownsville.

Flash Flood in CAMERON, TEXAS
From 01-OCT-21 17:15:00 to 01-OCT-21 20:15:00 (CST-6)
Location: PORT BROWNSVILLE
Flood cause: Heavy Rain
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

Picture received from the public of a vehicle partially submerged in flood waters near the intersection of FM 511 and State Hwy 48.

Flood in WILLACY, TEXAS
From 01-OCT-21 14:30:00 to 01-OCT-21 16:30:00 (CST-6)
Location: YTURRIA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Department of Highways

TXDOT reports standing water on I-69E/US-77 near and north of the business 77 split roughly 4 miles north of Raymondville.

Flood in HIDALGO, TEXAS
From 01-OCT-21 14:30:00 to 01-OCT-21 17:30:00 (CST-6)
Location: SAN JUAN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Picture received from the public of portions of the I-2 Frontage Road under several inches of water. Exact depth unknown at this time.

Flood in HIDALGO, TEXAS
From 01-OCT-21 14:45:00 to 01-OCT-21 17:45:00 (CST-6)
Location: PROGRESO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

The Weslaco Chief of Police reported 2.19 of rain, with 1.5 falling in one hour. Several reports of street flooding were passed on with water starting to top curbs.

Flood in CAMERON, TEXAS
From 01-OCT-21 15:00:00 to 01-OCT-21 18:00:00 (CST-6)
Location: PALMETAL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Report received from public of several inches of water topping the curbs at the intersection of Business 77 and Harrison Road in Harlingen.

Flood in CAMERON, TEXAS
From 01-OCT-21 15:45:00 to 01-OCT-21 18:45:00 (CST-6)
Location: PALMETAL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Picture received from public of Madison Ave in Harlingen under several inches of water. Exact depth unknown at this time.

Flood in CAMERON, TEXAS
From 01-OCT-21 16:00:00 to 01-OCT-21 19:00:00 (CST-6)
Location: HARLINGEN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video received from public of water reaching up to car bumpers along Washington Ave between Commerce and 1st Streets in Harlingen.

Flood in CAMERON, TEXAS
From 01-OCT-21 16:15:00 to 01-OCT-21 20:15:00 (CST-6)
Location: PALMETAL
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video received from the public of water covering US-77/Sunshine Strip near the VA Health Center in Harlingen. Water was reaching up to the bumpers of some sedans.

Flood in CAMERON, TEXAS
From 01-OCT-21 16:30:00 to 01-OCT-21 19:30:00 (CST-6)
Location: LOS FRESNOS
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Picture received from the public of water halfway up the wheel wells of several cars in Los Fresnos near the library.

Flood in CAMERON, TEXAS
From 01-OCT-21 16:30:00 to 01-OCT-21 20:30:00 (CST-6)
Location: PORTWAY ACRES
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Public report of several inches of water flooding the intersection of Boca Chica Blvd and Central Ave.

Funnel Cloud in CAMERON, TEXAS
From 01-OCT-21 10:30:00 to 01-OCT-21 10:45:00 (CST-6)
Location: PALMETAL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Video received from public of a tropical funnel cloud near Exit 23A on I-69E in Harlingen.

Thunderstorm Wind in CAMERON, TEXAS
From 01-OCT-21 18:55:00 to 01-OCT-21 19:10:00 (CST-6)
Location: (BRO)BROWNSVILLE ARP
Magnitude: 48.00 EG
Property damage: 0.50K
Crop damage: 0.00K
Reported by: NWS Employee

NWS Employee reports tree down on North Indiana Ave just north of Boca Chica Blvd near Rick's Auto Service.

Flash Flood in CAMERON, TEXAS
From 01-OCT-21 16:30:00 to 01-OCT-21 20:30:00 (CST-6)
Location: PORT BROWNSVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Flooding along Ruben Torres Blvd. during the peak of the evening commute, and the result of an estimated 3 to 4 inches of rain per hour for two hours, stranded dozens of vehicles under up to 3 feet of water. A report of 4+ feet of water was obtained from a worker at the Circle K gas/convenience store at the intersection of Ruben Torres and N. Central Avenue during the peak of the flood shortly after 9 PM on the 1st.  Other structures had some flooding, including homes just south and north of Ruben Torres.  Damage values were unknown as of this writing.

Flash Flood in CAMERON, TEXAS
From 01-OCT-21 16:30:00 to 01-OCT-21 20:30:00 (CST-6)
Location: PORT BROWNSVILLE
Flood cause: Heavy Rain
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Public

Several reports of significant flooding along FM 802/Ruben Torres Blvd in Brownsville. This includes multiple reports of stranded vehicles near the WalMart, as well as between Robindale Blvd and Central Ave.

Flash Flood in CAMERON, TEXAS
From 01-OCT-21 18:00:00 to 01-OCT-21 21:30:00 (CST-6)
Location: (BRO)BROWNSVILLE ARP
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A resaca overflowed its banks along Vermillion Avenue, from 1 to 1.5 miles north of the intersection with Boca Chica Blvd. (State Road 4).  At least three feet of water likely occurred toward the end of the heavy rainfall, where an estimated 3 to 4 inches fell per hour for two hours between 5 and 6 PM CST on the 1st.  A CoCoRaHS observer along Vermillion Avenue reported more than 10 inches on the 1st, with most falling during this period; the two-day total was 13.53 inches.