It almost never rains in Las Vegas, and when it does flash flooding can occur. One place that is almost certain to have flooding during a storm is The Linq hotel parking garage. This spot has been prone to flooding for years, dating back to when it was the Imperial Palace.
I was watching the latest TheTrooper97 vlog video and he captured some of this flooding from last week at the 3:21 mark:
I also found another YouTube video from back in July that shows the overflow:
These videos make the Linq parking garage river look pretty dramatic, but I'm guessing this happens frequently enough that the staff knows how to re-direct traffic away from the rushing water.