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Workers at a farm saw hundreds of cactuses sweep away in a flood. Drivers on Arizona's main north-south freeway watched in shock as muddy waters submerged the road. Rescuers across the state rushed to save people trapped in cars and homes.

The Phoenix area was battered by torrential rain storms Tuesday that caused severe flooding across the desert region. The National Weather Service said some areas received more rain Tuesday than they had all last summer.

"It looked absolutely devastating," said Gov. Jan Brewer, who was glued to the TV all day watching the rescues. "For the last 10, 15 years, we've never seen anything the likes of this."

A helicopter crew rescued two women and three dogs from a home surrounded by swift-moving waters in a town about 30 miles north of Phoenix, while elsewhere a small trailer park was evacuated, a school was flooded and first-responders pulled motorists from partially submerged vehicles.

The National Weather Service issued a flash flood warning for much of the metro area and north of the city, where up to 8 inches of rain fell by midday in some of the mountainous regions along Interstate 17, the main north-south freeway in Arizona.

A river of muddy water rushed down I-17 about 25 miles north of Phoenix as motorists changed lanes to avoid the deluge. A stretch of freeway was shut down and reopened later in the day.

Parts of two other state highways closed because of flooding reopened Tuesday night, the Arizona Department of Transportation said.

In another dramatic rescue, authorities pulled an elderly woman from a van stuck in rushing floodwaters, a scene repeated across the region throughout the day as other motorists became trapped.

Officials said nearly 5 inches of rain fell around the town of New River, where a helicopter dropped two rescuers onto the roof of a home where someone inside had been waving a white piece of fabric from a window to draw attention. The rescuers later walked the women and dogs to safety as the water receded.

Kathy Mascaro said her typical 15-minute commute from home to work in the Phoenix area more than doubled because of the traffic caused by the flooding.

"It's crazy. You'd think, how could the desert flood, but it really does," Mascaro said. "I've never seen it this bad. I've been here over 20 years and it has never flooded this bad."

The Cox Cactus Farm in Phoenix was inundated by a nearby creek as rushing waters sent workers scrambling to save their more than 600 varieties of plants, shrubs and cactuses.

"Everything just washed away," employee Mitch Bell said. "There's nothing we can do."

The desert around Phoenix sees very little rain most of the year, so when storms roll through with such intensity as they did Tuesday, the water has nowhere to go.

"With so much rain falling so quickly, the water doesn't have a chance to soak into the hard-packed rocky soil," meteorologist Gary Woodall of the National Weather Service said.

Arizona's monsoon season runs roughly from June to September, when powerful storms form with heavy rain and whipping winds. It's a phenomenon that occurs each summer when the winds shift, bringing moisture north from the Pacific Ocean and Gulf of Mexico to produce radical and unpredictable changes in the weather.

Sporadic storms were expected to continue across the Phoenix area for the next few days, according to the weather service.

On Tuesday morning, rocks washed down a hillside onto I-17 about 60 miles north of Phoenix, causing several vehicle collisions, but no deaths or major injuries have been reported, said Bart Graves, a spokesman for the Arizona Department of Public Safety.

Meanwhile, residents of a small trailer park in Black Canyon City along a river about 40 miles north of Phoenix were evacuated late Tuesday morning, according to the Yavapai County Sheriff's Office.

There was minimal flooding damage to the park, but authorities wanted to get residents to a safe location because water had damaged roads, sheriff's spokesman Dwight D'Evelyn said.

Firefighters from Phoenix and the Daisy Mountain Fire District on Phoenix's northern outskirts rescued at least six motorists in separate incidents, Phoenix Fire Capt. Benjamin Santillan said.

"We've got units jumping from one car to the next to the next," Santillan said, adding that there were no reports of injuries.

Flights from Phoenix Sky Harbor International Airport were delayed up to two hours while some inbound planes were diverted to other airports until the storms passed.