Sep 3, 2018
A weak upper level low moved into Texas from the Gulf of Mexico and interacted with a very moist environment. Precipitable water values across South Central Texas were above two inches. When a low level jet developed overnight, this combination was sufficient to produce heavy rain that led to flash flooding. There were rainfall reports of 10.18 and 9.25 inches in the extreme northern part of San Antonio.
Source: NOAA National Weather Service Storm Events Database (event 783791). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Bexar County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.