The National Weather Service extended a flood watch until midnight in the Houston area after a morning and early afternoon of between half an inch and more than three inches of rain rolling through the area and an urban and small-stream advisory watch for the west part of Harris County up to Beltway 8, extending through Fort Bend County and to Colorado County, meteorologist Kent Prochazka said. 

Until about 3 p.m., the previous 12 hours in the Houston area saw the greatest amount of rainfall surrounding downtown and areas inside the 610 Loop. The heaviest rain fell in Wharton at 3.21 inches, Katy at 2.64 in the Brazos River off Interstate-10 west of Brookshire at 3.2 inches. The average inside the Loop was about half an inch.

The South Mayde Creek just west of Highway 6 was overflowing over its banks and has caused some flooding along the roads.

Although there is not an official accident count, there has not been a noticeable bump in law enforcement responding to weather-related accidents, Sanchez said.

There were three high water areas as of 3 p.m., including the Hardy Toll Road at Aldine Mail Road, Interstate-10 at Lockwood and the 610 East Loop northbound at Clinton.

As of 3 p.m., CenterPoint reported that 14,936 customers were without power.

Some of the hardest-hit areas are Jacinto City, Pasadena and along Interstate 45 south of downtown Houston.

Major outages also were reported north of Little York Road, between the Hardy Toll Road and U.S. 59, according to CenterPoint.

Though the weather has promised to improve Thursday, with the chances of rain dropping significantly, a cold front is coming through this weekend, according to the weather service. Thunder and lightning are possible Sunday that could potentially affect Houston's marathon.