Thunderstorms on Saturday led officials to temporarily close some roads.
Las Vegas Fire and Rescue spokesman Tim Szymanski told the Las Vegas Sun that rescuers received calls about water 4 to 5 feet deep in the Rainbow subdivision of Mount Charleston.
The area, which is northwest of Las Vegas, is where a massive wildfire burned in July and forced people to evacuate their homes.
One caller reported at least three people were trapped in cars and several others were stuck on decks outside their homes, Szymanski said.
Szymanski said rescue crews were on their way but did not have further details.
State Routes 156, 157 and 158 were temporarily closed on Mount Charleston on Sunday, Nevada Highway Patrol Trooper Jeremie Elliott said.
Earlier reports said troopers were discouraging anyone from driving up the mountain if they didn't need to, but Elliott said that wasn't the case Sunday afternoon.
"I think the rain let up so we were able to get the completely open for everybody." Elliott said.
The National Weather Service has issued a flash flood warning for southern parts of Nevada and Utah on Sunday.
Officials say there's a potential for showers and thunderstorms through Sunday evening which could result in flash flooding and possibly an inch or two of rain in some areas.
The National Weather Service has issued a flash flood warning for Clark County and Nye County through the afternoon.
A flash flood watch has been issued for parts of Clark, Lincoln and Esmeralda counties and the Lake Mead and Red Rock Canyon areas through Sunday night.
In southwest and south central Utah, a flash flood watch is in effect through Sunday night for the Zion National Park and Glen Canyon areas.
Meteorologist Mike Kennedy told the Las Vegas Sun that the Las Vegas area has had unusually high levels of moisture in recent days, and officials expect any storms to produce a lot of rain.