Why California’s County Fire has rapidly spread through wine country

Fire has returned to California’s wine country as the flames thrive on bounties of parched land. 

The County Fire began on Saturday afternoon and since then has devoured over 1,000 acres of land each hour. As of Tuesday morning, the Golden State’s largest fire had spread over 70,000 acres in Yolo County and into the edges of Napa County.

The return of fire to the region, which cast ominous, orange glows over San Francisco to the south, is especially unwelcome after last October’s firestorms in the region, which were the deadliest in the state’s history. 

But such a fire — ultimately produced by a grim mix of dry land, hot temperatures, and gusty winds — wasn’t unexpected. 

Fire managers knew there was “significant fire potential” here. Any spark could turn into a nasty conflagration due to the exceptional amount of parched vegetation, or fuel, just waiting to burn.

“There’s indications we have record fuel loading right now,” Brenda Belongie, lead meteorologist of the U.S. Forest Service’s Predictive Services in Northern California, said in an interview. “There’s lots of dry grasses.”

“Grass is a big fire curator,” said Belongie. “You add wind to that and you’ve got a good combination.” 

In the short term, grasses have just shot up this April, when the region received some much-needed rain after a drier winter. 

“Timing is everything, said Belongie. “We got rain in April which allowed the grass crop to just explode.” 

But grasses in past years have also proved to be big fuel contributors. Specifically, an abundance of grasses and other vegetation from the previous winter (2016-2017) were left to burn. This vegetation flourished after that profoundly rainy winter, one of California’s wettest on record. 

And that winter was followed by another extreme: The state’s hottest summer ever recorded. All this vegetation proceeded to dry out, and was then followed by April’s growth.

“It’s last year’s leftovers and this year’s additions,” said Belongie.  

A caravan of fire trucks en route to the County Fire on July 2, 2018.

But that’s not all. 

Much of the land burned by the Country Fire, as well as the Pawnee Fire to the north, “has not burned in decades,” Gregory Giusti, a former forestry researcher for California’s Division of Agriculture and Natural Resources, said over email. 

In short, decades of built-up vegetation, or fuel, has not been naturally thinned out by normal wildfire events.

“I don’t believe any of the acres currently burning have been impacted by the past fires so the fuel loads [grasses and vegetation] are heavy,” said Giusti.

The result of all this fuel, combined with weather conditions, has proven incendiary.

“This is certainly unprecedented fire growth for this time of year,” Gabe Lauderdale, a public information officer for Cal Fire, the state’s fire protection agency, said in an interview. Lauderdale notes that later in the season, like September, is when the land is even drier and more susceptible to large fires.

A fire like this in early July, however, “is not unknown,” said Belongie. Along with dry fuel and the shape of the land (“fire loves to run uphill”), the third factor of windy or hot weather can come at anytime, and stoke surges of fire. 

“Weather is like the two-year-old in the group — it’s constantly changing,” she said. 

Fortunately, the land burning so far is largely undeveloped. 

“Though that is no comfort for those who do live the in fire’s path,” said Giusti.

California may be increasingly susceptible to loads of dried-out grasses in the future. Climate scientists say to prepare for periods of alternating extremes of grim drought and winter deluges — just like the abrupt transition from the state’s worst drought on record (2012-2016) to a winter rife with flooding. 

This means loads of vegetation will shoot up, but might soon become parched for years at a time under the famously sunny, and often cloudless, California sky.