A 4,000-acre wildfire raging near Lake Berryessa in Napa County has forced evacuations and is threatening 150 structures in the Quail Ridge Community, officials said Wednesday evening.

The Wragg Fire, which started after a vehicle accident, broke out about 2:30 p.m. and spread “at a rapid rate,” pushed by erratic winds, said the California Department of Forestry and Fire Protection. By 7:30 p.m., it was burning across 1,000 acres, Cal Fire said.

Structures were also threatened in the Mix Canyon and Cold Canyon areas south of Lake Berryessa, Cal Fire said. Residents there were told to evacuate.

At 9:20 p.m., the fire was only 5 percent contained and had jumped Putah Creek near Winters.

“The fire is traveling at a rapid rate of spread. The terrain is brush covered, rugged and steep, with difficult access. Winds are erratic,” Cal Fire officials said.

Cal Fire spokeswoman Lynne Tolmachoff said that there was no estimate for when the blaze would be contained but that it would help crews significantly if the winds died down.



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At least fifteen engines, six air tankers and four helicopters were fighting the fire.

The Wragg Fire was not among more than 40 wildfires around California that were caused by lightning strikes over the past couple of days. Most of those fires are in the Sierra and were contained within a few hours, Cal Fire said. The largest, a 24-acre blaze in Siskiyou County called the Dorris Fire, was contained late Wednesday.

Many of the 4,000 lightning strikes across Northern California reported since Tuesday were not accompanied by rain, raising the fire danger significantly.

“The drought has absolutely led to drier-than-normal conditions,” said Cal Fire spokesman Dan Berlant. “It doesn’t take much for a fire to start.”

The Red Cross has opened an evacuation center for Wragg Fire evacuees at the Winters Community Center, 201 Railroad Ave., Winters (Yolo County).

Jenna Lyons is a San Francisco Chronicle staff writer. E-mail: jlyons@sfchronicle.com