The National Weather Service in League City issued a Flash Flood Watch from 7 p.m. Tuesday through Wednesday morning.
"A line of strong thunderstorms will develop over southeast Texas this evening and slowly move eastward through Wednesday morning," the NWS statement says. "A combination between the slow-moving nature of the thunderstorms, back building/training of thunderstorms, and recent rainfall over the area has led to an increasing threat of flash flooding."
The NWS statement said rainfall can range around one to three inches per hour but that could increase.
"There remains some uncertainty in the timing and location of the line of strong thunderstorms," the statement says. "On average, two to four inches of rain is expected through tomorrow morning with isolated areas of six to eight inches possible."
The rainfall could make low-water crossings unpassable and cause small creeks and bayous to rise, the NWS said.
Areas affected included Austin, Colorado, Fort Bend, Waller, Washington and Wharton Counties among others in coastal and inland parts of Harris, Matagorda and Galveston Counties.
The Tuesday afternoon statement concluded by advising residents to monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued.