Police have confirmed that a woman's body was found in floodwaters Saturday behind a store.
A car had been found abandoned after being swept underneath a bridge into a culvert, but it isn't known whether the woman had been in that car.
"Our officers and firefighters are doing a great job of monitoring the various closures and keeping the public safe," San Antonio police Chief William McManus said. "I've been kept abreast of literally hundreds of high water rescues and at least one tragic death due to swift water."
Two other vehicles were stuck on the same street where the body was found. Water rescues there were successful, and no one was injured.
"The best thing people can do is to limit travel only to that which is absolutely necessary and to stay tuned for updates," McManus said.
San Antonio firefighters have pulled people from submerged cars and rescued passengers whose bus was swept away in flood waters from torrential rains.
Officials say numerous roads have been closed because of flash flooding.
The San Antonio Airport had recorded nearly 10 inches of rain in the past eight hours or so.
The National Weather Service says rain continues falling at a rate of 2 inches per hour in several counties.