A critical flash flood event began Saturday night in the central and southern United States and escalated into a life-threatening situation for many in parts of Oklahoma and Texas — a region already swollen with well-above-average rainfall this month. The torrential late-May rainstorm is pushing some southern cities toward their wettest May on record.

Flash flood watches and warnings stretch from southern Texas to Missouri as a trough of low pressure digs across the southern United States. As much as 10 inches of rain has fallen in central Texas, flooding rivers well beyond their banks. Three to six inches of rain has fallen in the Dallas-Fort Worth metro area, and more heavy rain continues to push through northern Texas.

The Blanco River around San Marcos, Tex., north of San Antonio, saw an incredible wall of water push through over the course of an hour early Sunday, rising 26 feet to reach a peak of about 43 feet.

“The Blanco River rose more than 33 feet in just 3 hours in Wimberley, Texas, reaching a level more than 27 feet above flood stage at 1 a.m. Sunday,” writes weather.com. “This broke the all-time record crest from 1929 by nearly 7 feet, before the river gauge stopped reporting.” The Blanco River is expected to remain in flood stage through Monday afternoon.

A flash flood emergency has been issued for the Blanco River basin and its tributaries in central Texas. A flash flood emergency, which the National Weather Service issues within a flash flood warning, is reserved for the most dangerous and life-threatening situations. The Weather Service in Austin is urging people to seek higher ground in these areas.

The storm sewer system overflowed in dramatic fashion around San Antonio’s popular riverwalk area. Water was exploding from the sewer covers and flowed down into the river as tourists stood by to take photos and video.

May is ending for the southern U.S. states the same way it came in — wet. On May 6, nearly eight inches of rain fell in Oklahoma City, making it the wettest May day on record for the location. The National Weather Service was forced to issue a flash flood emergency for the first time in the history of the office. There was so much water pouring from the sky over central Oklahoma that tornado shelters began to float up out of the ground.

As of Saturday night, Oklahoma City topped its previous record May rainfall of 14.66 inches set in June 1989.

Parts of Texas, which has been in a critical drought situation for years, have seen well-above-average rainfall for the month. Widespread areas of the state have seen rainfall as much as 10 or even 20 inches above normal for the month.

With total monthly rainfall over 10 inches and climbing, Dallas-Fort Worth moved into at least its fourth wettest May on record. The wettest May in Dallas-Forth Worth occurred in 1982, when 13.66 inches fell. In addition to seeing its second-wettest May on record, Lubbock, Tex., is also pushing toward its wettest year-to-date on record, over 10 inches above average. Lubbock’s month-to-date rainfall total is 8.32 inches, while its rainiest May on record stands at 12.69 in 1941.

As of Thursday, the U.S. Drought Monitor said no portion of Texas — or Oklahoma, for that matter — is in an extreme drought anymore. Victor Murphy, the climate program manager for the National Weather Service’s southern region, said the extreme Texas drought is “all but over.”