Maps from the Northern California Geographic Coordination Center show areas of the north state with above-normal significant fire potential from June through September and October 2021.Northern California Geographic Coordination Center

Kellie Hwang June 4, 2021Updated: June 4, 2021 9:48 p.m.

Northern California’s impending wildfire season is looking more and more grim by the day.

The outlook for fire potential is above normal for much of the region through the summer, and by fall, virtually all of Northern California will be under serious threat, according to the most recent report and maps from the interagency Northern California Geographic Coordination Center.

The extremely paltry rainy season has resulted in more than half of the region receiving below 50% of average rainfall, leading to widespread drought conditions, with most of the state now in extreme or exceptional drought.

Stephen Leach, a fire weather meteorologist for the U.S. Bureau of Land Management who identifies high-risk weather patterns that influence wildfire potential in Northern California and northwest Nevada, said the fire risk is coming earlier than usual this year.

“All areas of Northern California are vulnerable for wildfire spread now, several weeks ahead of normal,” he said. “The higher-elevation timber areas have the dry fuels in place, and ignitions are becoming a bigger threat for large fire occurrence. At lower elevations, including the Bay Area, trees and brush are very stressed and will become flammable a lot earlier than usual.”

According to the outlook, grasses and weeds have dried several weeks ahead of schedule, and the lack of brush growth may lead to dead outer branches and leaves, increasing their flammability. The only silver lining is that with the lack of rain, grass and weeds came in lighter than usual, which will mean grass fires can be controlled more easily, Leach said.California Wildfires

Leach said the report shows that the northern third of the state has experienced its driest rainy season in more than 20 years.

“That means that soils are extremely dry and fuels, both live and dead, are setting records for dryness for this time of year,” he said. “We are seeing fuel moisture values near peak fire season values that we would see in a normal year.”

Leach said the worst-case scenario would be a situation similar to last August’s, with a “lightning siege” causing many ignitions all at once — but such an event is “very rare.”

“For the Bay Area, late summer and fall offshore wind season will combine with the very dry fuels to push the significant fire potential to above normal,” Leach said. “At this point, all of the pieces are in place for an active fire season.

“It all depends on the ignitions, however,” he added. “And most fires in California are human-caused. So, with luck and everyone’s careful and thoughtful behavior in the outdoors, it could still be a fire season without catastrophic fires.”Kellie Hwang is a San Francisco Chronicle staff writer. Email: Twitter: @KellieHwang