Massive Monsoon Rainstorm Thrashes Phoenix Roads, Floods Freeways

Dark skies on Tuesday afternoon gave way to heavy rain across most of metro Phoenix, hitting the central Phoenix area at about 5 p.m. and making life tough on thousands of commuters.

The monsoon storm caused epic flooding across the Valley, reminiscent of a similar deluge two years ago. Vehicles on Interstate 17 became stranded in the rising waters, and Interstate 10 near State Route 51 was also flooded. On many Phoenix streets, cars plowed through water several inches deep.

City of Phoenix officials said street crews had to reposition manhole covers that had been lifted up by stormwater. Several rescues of motorists were reported, including that of an elderly woman who had to escape her stalled vehicle at Third Street and Carefree Highway.

Yet remarkably, no one appears to have been injured.

Even after the rain abated, authorities recommended that drivers avoid stretches of Camelback and McDowell roads, as well as a stretch of 35th Avenue between Glendale Avenue and Camelback Road.

Not surprisingly, the evening's most impressive rainfall total was recorded near Camelback Road and I-17: 2.91 inches, says Matthew Hirsch, a meteorologist with the National Weather Service in Phoenix. To put that into perspective, until Tuesday, the Phoenix area had received an average of 2.33 inches so far for the entire year.

But wait — it gets even more amazing: About two inches of that total fell in just 37 minutes, and most of the 2.91 inches had fallen after one hour, Hirsch says.

"Yeah, it's pretty exceptional," he says. "I'm not sure if it set a record."

The NWS observed one to two inches of rain socking widespread areas from Scottsdale to central Phoenix, in the north Valley communities of Cave Creek and Anthem, and in parts of the East Valley. Some portions of north Mesa received 1.5 inches.

Like many monsoon storms in Arizona, this one was very selective about where it chose to dump. The official observation point at Phoenix Sky Harbor International Airport recorded a minuscule 0.15 inches. And if you saw lightning and apocalyptic skies all around you but only felt a couple of drops of rain on Tuesday evening, you must have been in Tempe.

A flood advisory throughout the Phoenix area remained in effect for much of the night, though heavy rain and flooding had subsided by 8:45 p.m., the NWS reported.

So what was responsible for the extra-nasty downpour?

"The atmosphere was exceptionally moist," Hirsch says. "We saw record moisture readings. A lot of humidity."

That muggy air will stick around for at least another day, adding to the chance for more thundershowers on Wednesday, Hirsch says.

Enjoy the cooler temperatures while you can. The mercury dropped below 80 by about 10 p.m. on Tuesday. But it's still summer, so won't last. The desert air is expected to dry out and climb back up to typical triple-digit temperatures starting on Thursday.