30 flash flood warnings: Inside Las Vegas’ unusual August

We saw it everywhere in August, from the Strip to Death Valley: The power of water.

Viral videos showed it raging through flooded hotel parking lots, pouring into casinos, and swamping roads in normally arid national parks.

Wetter and cooler was the weather for Southern Nevada in August, as a robust monsoon season rolled in and stubbornly persisted, forecasters said.

Harry Reid International Airport saw 0.61 inches of rain in August, almost double the August 30-year average (from 1991 to 2020) average of 0.32 inches, said Jenn Varian, a meteorologist with the Las Vegas office of the National Weather Service.

Temperatures were also cooler than normal, but not record-breaking. As of Monday, this month was in a three-way tie for the 13th coolest August in record Las Vegas history along with 2005 and 2013.

“The average high so far this August has been 100.1 degrees, which is notably cooler than the previous August,” said Matt Woods, also a meteorologist with the Las Vegas office of the National Weather Service. “Last year the average was 104.1 degrees, and in 2020 the average was 107.3 degrees.”

Thirty flash flood warnings were issued for Clark County in August, Woods said.

That total is significantly higher than most Augusts in the past 36 years, according to an Iowa State University website that tracks the issuing of National Weather Service watches, warnings and advisories going back to 1986.

But the more flood warnings in recent years doesn’t necessarily mean it’s been raining more lately.

How flash flood warnings have been issued has changed over the decades, particularly since 2007.

That’s when forecasters moved away from the practice of watching a storm approach and then issuing one catch-all flash flood warning for Clark County. Now, forecasters might issue multiple flash flood warnings in Clark County for different locations and times, which means more warnings being issued overall.

“It’s hard to say if its truly weather or not,” Woods said. “The criteria for warnings has changed quite a bit over the years.”

Only two other years have seen 30 or more flash flood warnings issued in August, and those were in 2013, when 30 were issued, and 2014, when 32 were issued. But that was also the time of the 2013 Mount Charleston Carpenter 1 fire, when forecasters were likely more apt to issue weather warnings for Mount Charleston and surrounding areas, both Varian and Woods said.

Unfortunately, this month’s flooding in the Las Vegas Valley has exacted a human toll.

Two men died in Las Vegas. One man who was pulled from a flood channel near the Strip on Aug. 11 died, and another man was found dead in the flood channel the next day.

A hiker who went missing in Zion National Park after flash flooding also was found dead.

The heat has also been deadly. Another hiker, a 31-year-old Southern California man, was found dead Saturday in Mohave County, Arizona, after showing signs of dehydration, according to the Mohave County Sheriff’s Office.

And there were also two rare tornado warnings issued on Aug. 21, with one confirmed twister in Arizona.

This month’s rain total is also up from the zero inches of rain recorded at the airport for the months of August in 2019, 2020, and 2021.

The record rain amount for August in Las Vegas was set in 1957, when an almost unfathomable 2.59 inches fell.

“It’s not the record wettest August by any means, but it’s been wetter than usual,” Woods said of this August.

The record cool August in Las Vegas was in 1983, when the average temperature was a still-balmy 95.2 degrees.

And if August seemed grayer than usual, that’s because the month had 19 partly cloudy days and one mostly cloudy day, said National Weather Service meteorologist Jenn Varian. Las Vegas is known to get about 300 sunny days a year.

As Sin City exits August with a heat wave, Woods said forecasters expect September to start off “warm with above normal temperatures,” prompting an excessive heat warning that will be in effect through 8 p.m. Sunday.

Contact Brett Clarkson at bclarkson@reviewjournal.com or 561-324-6421. Follow @BrettClarkson_ on Twitter.