Police and fire vehicles could be seen surrounding the library compound in the morning, and helicopters flew low overhead, dropping water and fire retardant on the flames. Heavy winds gusting to more than 60 miles an hour made it difficult to walk at times, and tumbled over museum signs that had been weighted with sandbags.

The blaze, named the Easy fire, began just after 6 a.m., which Mark Lorenzen, chief of the Ventura County Fire Department, said was “about the worst time it could happen” because of the strong winds and dry vegetation that was “ripe and ready to carry fire.”

Between 8 and 10 a.m., the fire tripled in size to cover 1,300 acres, putting more than 26,000 residents in evacuation zones, most of which are mandatory, according to Sheriff Bill Ayub. The fire is threatening about 7,000 homes in parts of the Simi Valley and Moorpark communities in the southern part of Ventura County, but no injuries have been reported.

Eric Tennessen, a chief with the Ventura County Sheriff’s Office, said deputies were knocking on doors and escorting people to safety. The evacuation area consists mainly of ranches, farms and a golf course, and is not densely populated, Chief Tennessen said.

Video from local news outlets showed smoke billowing from several distinct parts of the fire along hilltops, with the flames fanned by the wind as the sun rose. Later in the morning, flames could be seen approaching suburban neighborhoods nearby, and the Fire Department said that as many as 6,500 houses were threatened by the blaze.