Over the weekend, nearly a month’s worth of rain fell in parts of Washington and daily rainfall records were set in Oregon, with totals ranging between 1 and 5 inches from the coast to the western slopes of the Cascades.
The precipitation has moderated activity for several fires in Northern California, including the Dixie Fire, which is now at 90 percent containment.
But the weather quickly shifted Sunday night with the arrival of gusty offshore winds that will usher in much drier air and higher temperatures this week. The winds present a fire risk for locations that saw little precipitation over the weekend, mainly in the Sacramento Valley and surrounding ridges in the San Francisco Bay area and Sierra foothills. Some areas that did receive rain may also rapidly dry out.
Red-flag warnings are in effect through 8 p.m. Monday for much of interior Northern California and through Tuesday morning farther east into the Sierra, including portions of the Caldor Fire. Gusts exceeding 50 mph were recorded on the ridge tops in the Bay Area overnight.
The Los Angeles area will also see elevated fire risk due to hot and dry conditions combined with weak winds.
Fires in and near Sequoia groves
This weekend’s storm system brought strong winds but no rain to blazes burning in the vicinity of giant sequoia groves in the southern Sierra Nevada. The KNP Complex and the Windy Fire, each more than 23,000 acres, have grown considerably since Friday.
However, firefighters’ efforts to protect the famed Giant Forest and General Sherman Tree in Sequoia National Park are progressing well, and there was minimal growth into that area Sunday.
“The fortunate thing is the Park Service has done a lot of prescribed burning in there since the 1960s, and so it’s making their job a lot easier,” Jon Wallace, operations section chief on the KNP Complex, said in an update Sunday morning. “As that fire came out of the brush and timber … and up into that Giant Forest, the flame lengths really dropped down to 2 or 3 feet off the ground.”
Farther south, the Windy Fire has burned into sequoia groves within the Giant Sequoia National Monument, including a portion the “Trail of 100 Giants” within the Long Meadow Grove. The popular hiking loop features over 100 towering trees that are up to 1,500 years old.
Giant sequoias, the world’s largest trees, grow in a narrow range of the Sierra’s western slopes. While the species thrives with low-to-moderate-intensity fire, extreme blazes can kill trees and permanently damage forests. This type of “high severity” fire has increased in Western forests in recent decades, fueled by climate change and poor forest health due to fire suppression and other factors.
“The fire behavior within the Long Meadow Grove has been light to moderate,” Seth Mitchell, operations section chief, said in an interview Sunday. “It’s very favorable fire activity and the trees stand a good chance of surviving.”
However, other groves had been directly affected by the Windy Fire, including the Peyrone Grove, which was fully within the fire’s perimeter. An initial assessment of any damage to the trees could take days to complete, according to an InciWeb update.
Most of interior California experienced its hottest summer on record in 2021. The current water year, which ends on Sept. 30, is the driest on record for the southern Sierra, according to a six-station precipitation index that includes the Giant Forest in Sequoia National Park. An average of just 9.9 inches of rain has fallen this year, which is less than the previous driest year, at 10.9 inches in 1976-1977. Average annual rainfall for the area is 28.8 inches.
Given summer heat and massive precipitation deficits, 45 percent of the state is in exceptional drought, the U.S. Drought Monitor’s most severe category, including areas at heightened fire risk this week.
Diana Leonard is a science writer covering natural hazards in California.