Environment & Science

Rain didn't do much to dampen fire risk in Southern California, experts say

Raindrops are seen on a vehicle's window in Arcadia on Dec. 2, 2014.
Raindrops are seen on a vehicle's window in Arcadia on Dec. 2, 2014.
Frederic J. Brown/AFP/Getty Images

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Los Angeles saw rain and cooler temperatures recently, but forecasters say we could get triple-digit heat this weekend and even dry, hot Santa Ana winds. That means an increased risk for fire across Southern California.

But, wait, what about all that rain?

Unfortunately, it wasn't enough to significantly cut the chances of a dangerous fire, according to David Gomberg with the National Weather Service. While some areas saw more than an inch of precipitation over the weekend, Gomberg said it takes much more water and more time to dampen fire fuels like chaparral shrubs.

"A lot of the moisture, it takes a while for it to really soak into the vegetation," Gomberg said.

He added that many of the areas most affected by Santa Ana winds, like Santa Clarita and the San Fernando Valley, didn't see that much rain compared to elsewhere.

Biologist Philip Rundel of UCLA said there’s another big factor increasing the chance of fire: dead plants.

"After four years of drought, we’ve had a huge amount of dieback, and that's dead tissue on all these chaparral shrubs," he noted.

That dead tissue isn’t decaying fast enough and will stay prone to fire even after heavy rain, because it doesn't hold water the way living plants do.

On top of it all, Gomberg says weather models indicate Southern California will likely see a few days of dry heat before the winds kick in, meaning plants will have time to transpire any gains in moisture, with that moisture evaporating.

So, fire risk this coming weekend will probably be about what it was before the rain fell, but Rundel said this storm was an encouraging sign.

"It’s a start” he said. “We need to get more.”