What to Know
- From January to early August last year, more than 3,660 wildfires burned a staggering 615,000 acres in California
- During that same period this year, about 2,900 wildfires have burned only 22,900 acres
- Soil moisture is 40 percent above average for most of California. In the LA basin and OC, it's 60 percent above average.
So far, California has been spared the large wildfires that ravaged the state in 2018, a year that included the largest, most destructive and deadliest wildfires on record in the Golden State.
From January to early August last year, more than 3,660 wildfires burned a staggering 615,000 acres in California. During that same period this year, about 2,900 wildfires have burned only 22,900 acres, according to CALFIRE statistics. California's five-year average for that period is about 3,500 fires and 245,800 acres of burned land.
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So, what's behind the significant decrease in the number of fires and acres burned? It's due to several factors, but one of the most important is soil moisture.
"If you’ve ever tried to make a fire with wet wood you know what I’m talking about," said NBC4 forecaster Anthony Yanez. "This same principal relates to fires getting out of control. As long as our fuel moisture remains above average, a rapid fire spread will be difficult to do."
Soil moisture is 40 percent above average for most of California. In the Los Angeles basin and Orange County, it's 60 percent above average.
The combination of steady winter rainfall, an active monsoon season and high humidity has kept vegetation full of moisture. More than half our summer we've had an onshore wind and that keeps humidity in place. Without dry brush that acts as fuel, fires can't spread as quickly.
The devastation wrought by fire in 2018 included the Mendocino Complex, a 459,000-acre wildfire that destroyed about 280 buildings in three Northern California counties. So far this year, the state's largest wildfire is a 14,000 blaze in Modoc County that's nearly contained.
In Southern California, there has been excessive heat this summer, but only for short periods, which also helps maintain soil moisture.
"So far, this fire season has been pretty quiet," Yanez said. "The bad news is once we get Santa Ana winds, it will dry us out quickly."
Santa Ana winds, produced by surface high pressure over the Great Basin squeezing air down through canyons and passes in Southern California's mountain ranges, are common in the fall and have a long history of fanning destructive wildfires in the region.
When it comes to acres burned, six of the state's 10-largest fires have burned in summer months. But fall is historically the worst time of the year for damaging wildfires in California. Seven of the state's 10-most destructive wildfires have occurred in October and November.
Since 1970, California is not only seeing more fires, but larger fires. Seven of the top 10 largest have all occurred since 2000. They are the 2017 Thomas Fire in Ventura and Santa Barbara counties; the October 2003 Cedar fire in San Diego County; the August 2012 Rush fire in Lassen County; the Rim fire in Tuolumne County in August 2013; the July 2007 Zaca fire in Santa Barbara County; the October 2007 Witch fire in San Diego County; and the Klamath Theater Complex fires that burned in June 2008 in Siskiyou County.