Monsoonal moisture from the tropics slammed the Phoenix area and other parts of the Southwest with heavy rainfall Tuesday.
By Tuesday evening, some locations had received more than 4 inches of rain, NOAA reported.
"There were slow-moving bands of heavy rainfall that tracked across the area, producing rainfall rates of more than 1 inch per hour," AccuWeather.com Meteorologist Brian Edwards said.
AccuWeather.com Senior Meteorologist Bernie Rayno said it is not unprecedented to get flooding in the Phoenix area, and cited various instances in which the region has been inundated by severe flooding since the late 1800s.
"This is not a set-up we see every year," Rayno said, referring to the monsoonal moisture which normally brings isolated thunderstorms to the area, and an upper low moving across California that contributed to focusing the storms just north of the area.
The combination of the focused storms, terrain and Arizona soil all worked together to provide the conditions for damaging floodwaters that swept across the region north of Phoenix, he said.
Several reports of flooding and water rescues were reported northwest of the Phoenix area, according to Phoenix Fire Department and Rescue officials.
Portions of Interstate 17 north of the city were inundated by floodwaters, which forced its closure. Several other roadways were also closed due to flooding, and there was a report of a rockslide along I-17, according to NWS spotters.
Edwards said the storms will continue into the evening hours before the weather quiets down later in the night.
"It's unusual to get rainfall rates that significant, but if it's going to happen, it will happen this time of year with the monsoonal moisture," he said.
Each year, moisture from the tropics sets in across the region.
"It occurs during the latter part of the summer and early fall, July to early September typically," Edwards added.
Ignacio has rapidly strengthened into a major hurricane as it tracks toward the Hawaiian Islands.
While Erika has weakened to a tropical rainstorm, downpours will still spread from Hispaniola and Cuba to Florida as August transitions to September.
As many as seven tropical cyclones were churning throughout the world this past week, while smoke from wildfires across the Pacific Northwest led to poor air quality across the region.
Heat will linger in Eastern Europe for much of the fall season; meanwhile, the British Isles and northwestern Europe can expect a stormy end to the season.
One of the most damaging natural disasters to hit the U.S., Hurricane Katrina battered areas along the Gulf Coast. Take a look at five scenes from the immediate aftermath to years later as the region worked to recover.
A stalled frontal boundary from southeast China through Taiwan and Japan will be the focal point for rounds of heavy rainfall into early next week.
Houston, TX (1980)
2.23 inches of rain fell in less than 1 hour. Streets were flooded in the downtown district and a tornado touched down briefly west of Houston at Sealy, TX.
Pittsburgh, PA (1982)
39 degrees, coldest ever in August.
Anchorage, AK (1989)
A total of 9.6 inches of rain -- wettest August on record.