From the National Weather Service:
The threat for locally heavy rain will continue today and a Flash Flood Watch is in effect for areas southwest of the Houston metro.
An image describing the Flash Flood Watch is attached.Isolated locations in western Harris County, Waller County, and Fort Bend County have received amounts between 3-5″ in the past 24 hours. This rainfall, in addition to persistent rain around the Matagorda Bay area, will result in the risk for rain today to produce minor or flash flooding in localized areas. Expect rainfall today to occur in waves; should rainfall move across the same area repeatedly with very little break in between these waves, the minor or flash flooding potential will be increased.
The system responsible for the past few days with intermittent heavy rain should begin to drop into Mexico and away from the region tonight, resulting in lower rain chances and the elimination of the heavy rain threat through the end of the week.