Texas, Oklahoma floods: 12 people missing as more rain forecast

Rescuers searched for 12 people, including three young children, on Monday after heavy floods swamped Texas and Oklahoma — and forecasters warned that more rain and damaging winds are on the way.

Authorities in Hays County, Texas, increased the number of missing to 12 from eight. They included members of two families in the town of Wimberley, three of whom are children under the age of 10, relatives told NBC News.

The small town sits on the Blanco River, which runs between Austin and San Antonio and was one of the worst hit areas by the weekend floods. Waters rose so quickly Sunday that roads turned to torrents, 1,000 people were forced to evacuate, and hundreds of homes were destroyed.

Three people were confirmed killed, two in Oklahoma and one in Texas.

In Broken Bow, Oklahoma, 13 people were trapped in a rental cabin on a river. The Oklahoma Highway Patrol said they were not in danger, but were stuck on an island when authorities opened the flood gates at a nearby lake and the water level rose.

Memorial Day events were canceled in the nearby city of San Marcos and a curfew was put in place there until daybreak Monday. The city said in a statement that the flooding was the "the most severe in recent memory."

"The flood waters are receding a little now but we're going to have another round of thunderstorms hitting again by mid-morning," said Weather Channellead meteorologist Kevin Roth.

In North Texas, including Dallas, forecasters warned of the possibility of the weather phenomenon known as a derecho — wind damage of more than 240 miles, coupled with wind gusts of 75 mph or greater. The threat was greatest for late afternoon.

Widespread heavy showers and thunderstorms could occur across most of Oklahoma, central and eastern Texas, Louisiana and Arkansas, Roth said, possibly including damaging wind gusts, hail and isolated tornadoes.

The storms were the latest in what has been a particularly wet year for the Plains, with several towns and cities already breaking their all-time wettest month records this May.

Records continued to tumble Sunday, with the 3.3 inches that fell in Dallas making it the wettest May 24 in 117 years. Oklahoma City added to what is already its wettest ever month, the 18.69 inches to fall this May far outweighing the 14.92 inches that fell in May 2013, according to The Weather Channel.

On Monday, flash-flood warnings stretched from the Texas-Mexico border to western Tennessee and northern Missouri. Much of Oklahoma was under a flood warning.

The Blanco River rose to 34 feet in just three hours on Sunday — its height of 40.2 feet breaking a record crest dating to 1929 by nearly six feet. The National Weather Service in San Antonio said the river was causing "catastrophic" flooding.

Across the nation, 21 river gauges were recording a "major flood" and 47 were showing "moderate flooding," most of which were in Texas and Oklahoma, according to Roth.

The weather system also triggered 36 reported tornadoes on Sunday in Kansas, Nebraska, Illinois, Colorado and Iowa, according to the National Weather Service. Roth said that while that twister threat would persist in some areas on Monday it would be significantly lower than over the weekend.

The storms were expected to calm significantly from Tuesday through Friday. Roth said that "while there will be storms around later in the week, they should be more hit-and-miss and the rainfall will be less impressive."