(Photo by Stina Sieg - KJZZ)

A flooded street in central Phoenix from Norbert rains.

(Photo by Julie Levin-KJZZ)

Rain approaches from the east Valley.

(Photo by Nadine Arroyo Rodriguez/KJZZ)

Phoenix residents Roger and Erin Shriner fill sandbags at the fire station near 19th Avenue and Dobbins Road.

The recent storms that have inundated the Valley originated from a unique combination of weather factors.

Tropical storms Norbert and Odile came from the same warm waters off the Pacific Coast of Mexico where another big storm is brewing. And if you think all this rain is rare, you’re right.

“It’s very unusual to see two or three eastern Pacific hurricanes in a row,” said state climatologist Nancy Selover. She explained how these rains are making it to the desert.

“If they hug the coast, that tends to enhance some of our monsoon stuff," Selover said. "So, it comes up the gulf of California, there’s very warm water there, and if it stays over the water, then it has the possibility of sending moisture up to us.”  

And one storm’s moisture may serve as another storm’s flood. Desert soil saturated from prior rain doesn’t absorb water well, and it releases moisture into the air between storms, increasing the chance for rain.

So even if just some rain falls on the Valley in the near future, the chances of flooding are even greater.