A massive dust storm descended on the Phoenix area in the U.S. state of Arizona, drastically reducing visibility and delaying flights as strong winds downed trees and left thousands of residents without power.

The dust cloud that moved across the Phoenix valley Tuesday night had formed in an afternoon storm in the Tucson area, and then rolled north across the desert before sweeping over the city like an enormous wave, said National Weather Service meteorologist Paul Iniguez.

Radar data showed the storm's towering dust wall had reached as high as 8,000 to 10,000 feet, or nearly 2 miles, he said.

"This was pretty significant," Iniguez told The Associated Press. "We heard from a lot of people who lived here for a number of storms and this was the worst they'd seen."

By the time the dust cloud neared the metropolitan area, it had started to dissolve but it still towered over the city with a wall of at least 5,000 feet, according to the weather service.

KSAZ-TV in Phoenix reported the storm appeared to be roughly wide in some spots. It briefly covered the city's downtown at around nightfall.

The storm was part of the Arizona monsoon season, which typically starts in mid-June and lasts through September.

The National Weather Service says strong winds with gusts of up to more than 60 mph in some places rapidly moved the dust cloud northwest through Phoenix and the surrounding cities of Avondale, Tempe and Scottsdale. More than a dozen communities in the area also were placed under a severe thunderstorm watch until 11 p.m.

Some 8,000 Salt River Project utility customers were left without power, KNXV-TV reported late Tuesday.

The Federal Aviation Administration said on its website that because of low visibility in the area, no Phoenix-bound flights were allowed to leave Las Vegas or Los Angeles airports until 9 p.m., and flights at the airport were delayed for about an hour.