HOUSTON -- Many Texas cities remain in danger though a barrage of deadly thunderstorms has tapered, as officials warn about the possibility of more flooding from rain-swollen rivers.

The storms and floods in Texas and Oklahoma this week have left at least 23 people dead and at least 15 others missing.

In suburban Houston, the rains have pushed the San Jacinto River above flood stage, and its waters were expected to cover streets in subdivisions along the west fork of the river, possibly stranding people in their homes for days if they don't leave.

In Wharton, about 60 miles (97 kilometres) southwest of Houston, the mayor asked residents to voluntarily evacuate about 300 homes on the west side of the city due to the predicted rise of the Colorado River. The river is expected to crest at about 45.5 feet (13.9 metres), nearly 7 feet (2.1 metres) above flood stage, by either late Friday or early Saturday.

"We've made a tour of the area, and a lot of the people have taken heed of our warnings and are moving out," Mayor Domingo Montalvo Jr. said. The city has opened a shelter, but so far only one person is staying at the facility.

In the Parker County town of Horseshoe Bend in North Texas, officials asked about 250 residents to leave their homes as the Brazos River was expected to rise above its flood stage of 21 feet (6.4 metres) on Thursday.

Meanwhile, in Central Texas, crews continued searching for nine people feared dead after the swollen Blanco River smashed through Wimberley, a small tourist town between San Antonio and Austin, over the Memorial Day weekend. In Houston, residents whose homes were flooded by torrential rains on Monday and Tuesday also continued their cleanup efforts.

While the Houston area got a respite from rainy weather for most of Wednesday, the heavy rains from earlier in the week were still making their way downstream. By late Wednesday, the San Jacinto was at 52 feet (15. meters), nearly three feet (one meter) above its flood stage, said Kim Jackson, a spokeswoman for the Harris County Flood Control District.

In Houston, between 800 and 1,400 homes have already been damaged by the flooding. Thousands of homes were also damaged or destroyed in the central Texas corridor that includes Wimberley -- 744 of them in San Marcos alone.

This has been the wettest month on record for Texas, even with several days left. The state climatologist's office said Wednesday that Texas has gotten an average of 7.54 inches (19.15 centimetres) of rain in May, breaking the old record of 6.66 inches (16.92 centimetres), set in June 2004. While rain is in the forecast the next couple of days for many of the affected areas, the chances for showers are greater during the weekend.