A surge of tropical moisture is turning parts of the Four Corners into a flash-flood zone, with heavy rain, flooding and water rescues reported across Arizona and New Mexico.

Arizona impacts

In and around Phoenix, flooded roads caused major problems Tuesday morning, including several water rescues by Maricopa County Sheriff's deputies.

Officials initially received reports that two box trucks had been swept away by floodwaters. When deputies arrived, they found one truck had been carried into a wash. The driver managed to escape safely and was not injured.

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Deputies also responded to a 911 call from a driver who attempted to cross a flooded roadway and became stuck. The driver was safely led out of the vehicle.

Later, authorities rescued a man who had climbed onto the roof of his vehicle after becoming trapped in a wash.

(MORE: Elderly couple rescued from flooding by helicopter)

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Flooding was reported across the Phoenix metro area, with some areas picking up an inch or more of rain in the past 24 hours, according to the Maricopa County Flood Control District.

A flash flood warning was in effect for isolated areas, while a flood watch was issued for Maricopa and Pinal counties.

New Mexico flooding

Farther east in New Mexico, flooding also reached dangerous levels. Drivers were filmed pushing through rising waters on roads that had nearly disappeared.

In Radium Springs, an arroyo became completely full and was flowing strongly after heavy rain, while nearby roads became impassable.

Water also surged across Highway 185.

What's fueling all this rain is unusual for this time of year.

“While we’re coming up on the end of the monsoon across the Southwest,” senior meteorologist Jonathan Belles explained, “the mixture of Hurricane Polo and a jet stream disturbance are set to bring a level of moisture rarely seen in September.”

(MORE: Hurricane Polo’s moisture to head toward Texas)

Widespread flood risk

That moisture is spreading across the Four Corners region, with the threat extending into Colorado and Utah, where heavy rain can quickly send water rushing through washes, especially in areas with saturated ground or burn scars.

Heavy rain also lashed southern Nevada on Monday. The National Weather Service issued a severe thunderstorm warning as water rushed across the Laughlin Riverwalk along the Colorado River.

Belles said the moisture will push into the Plains and Midwest in the coming days, shifting the threat eastward after soaking the Southwest.