Environment & Science

How much rain did SoCal receive this winter? Not much at all

Rain falls over Pasadena on Tuesday, Jan. 5, 2015. A series of storms is expected to dump up to six inches of rain on the Southland this week.
Rain falls over Pasadena on Tuesday, Jan. 5, 2015. A series of storms is expected to dump up to six inches of rain on the Southland this week.
Maya Sugarman/KPCC

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It's the last day of March, which means it's the end of the six-month period during which Southern California receives most of its rain. So, during this El Niño winter, how much rain did the region get?

Not much at all. 

A number close to 100 would mean it had been a typical year for precipitation—and this year the L.A. area is still about 40 percentage points below that. With just a few hours left in March, it will be impossible to make that up.

"The L.A. Basin has been incredibly dry this year," said David Pierce of the the Scripps Institution of Oceanography at UC San Diego, who created the rain metric used by KPCC.

"If you look at the statewide precipitation totals there's sort of a bullseye of dryness between, say, Oxnard and Mission Viejo, and it's really an outlier compared to the rest of the state," Pierce said.

The 58.7 percent figure factors in data from 2o weather stations across greater Los Angeles. They stretch from coastal locations including Newport Beach and Santa Barbara to inland ones in Redlands and Mount Wilson. Those stations are weighted according to geography and historical weather information.

This year, the L.A. Basin didn't see many rainstorms, Pierce said. And since just a handful of storms make up a the lion's share of the region's precipitation, that matters.

Other urban areas, including the Bay Area and San Diego, were also fairly dry this winter.

Thankfully, not everywhere in California was so dry. Statewide, Pierce's data show California received 108.4 percent of a normal winter's precipitation, with much of that moisture in the Sierra Nevadas. That has helped improve the snowpack and reservoir situation in Northern California, compared to a year ago.

And while the last six months have been unusually dry for Southern California, there's still some hope for April. Pierce said three of the last five strong El Niños saw April storms in SoCal.

"So, you know, it's possible," Pierce said. "It's not something you'd want to gamble a lot of money on."

You can trace Southern California's rainfall over the last six months using the chart below. This year is represented by the orange line.