Some people were seen being rescued from their cars by firefighters amid knee-deep water.
At the Circa Resort & Casino, visitors' cellphone videos showed water pouring from the ceiling and through a massive monitor in the sports book area.
[Ads /]
The flooding comes during the heart of monsoon season. Sometimes desert areas in the Southwest can see all of their annual rain in just a few days.
But Las Vegas has been even drier than usual, leaving the parched soil to act like concrete during a night of heavy rainfall.
[Ads /]
Meanwhile, in Kentucky, at least 16 people have been killed amid devastating flooding, Gov. Andy Beshear said Friday, and he expects that number to "get a lot higher."
More than 294 people have been rescued from floodwaters in eastern Kentucky so far, and that number will likely rise, Beshear said.
ABC News contributed to this report.