Environment & Science

Will this rain finally end Southern California's prolonged fire season?

Droplets splashing off a rain barrel.
Droplets splashing off a rain barrel.
Stock photo by J. Michael Darby via Flickr Creative Commons

Listen to story

Download this story MB

Southern California is getting a much needed soak, but will it be enough to end a prolonged wildfire season?

According to CAL FIRE's Mike Mohler, the area needs 3 to 4 inches of rain to saturate the soil and chaparral enough to significantly decrease the chances of a major fire.

Forecasters expect up to 5 inches to fall in parts of the region over the next day or so.

If that happens, Mohler says CAL FIRE will be able to reduce staff and idle some equipment in Southern California for the first time in nearly two years.

Last winter there wasn't enough rain for the fire agency to safely cut back the number of firefighters from peak levels.

"We haven't seen a wetting storm like this for years," he said. "And then you compound the drought on top of it, we really haven't gone out of peak [staffing levels]."

One reason this period of increased fire danger has lasted so long is that the drought has left a lot of dead chaparral on the hillsides.

"We have a lot of dead fuels, they don't absorb moisture like a live fuel would," Mohler explained.

That means it takes even more rain to soak these branches and leaves to the point where they won't ignite easily.

Once the storm has passed, CAL FIRE will take samples of both live and dead plants to test their moisture levels by heating them to see how long it takes for them to burn.

If the moisture is high enough, CAL FIRE will enter "winter preparedness mode" and store some fire engines and aircraft until next summer. Some seasonal firefighters will also be laid off for the winter.

Richard Minnich, fire ecologist with UC Riverside is confident that this downpour will be the drenching that will finally end the long season of heightened fire risk in Southern California.

"Plants will moisten up to the point where they are relatively non-flammable," he said, adding that it will likely take more than a month of arid conditions for plants to use up all the expected moisture.

If occasional rains continue through the winter, Minnich thinks the fire risk will likely remain low until June or July, when plants typically dry out after growing and flowering in the spring.

However, Rick Flores with the L.A. County Fire Department pointed out that lately, California's weather has been prone to extremes.

He said if the region gets a blast of warm, dry air, things could change.

"We don't know how long our rainy season is going to last, it could dry up and we could have another heatwave."

In fact, the Colby Fire which burned nearly 2,000 acres this past January occurred at a time when California is typically wet.

For now, fire officials plan to stay on alert until this storm has passed. In about a week CAL FIRE expects to announce whether or not they will reduce staff and store some equipment.