By Dan Whitcomb

LOS ANGELES (Reuters) – California firefighting crews may face on Thursday another round of fierce gusts that have fed a volatile wildfire, one of the largest in the state’s history, as they protect homes from flames and build control lines.

The so-called Thomas Fire, already the state’s fifth-largest blaze of its kind on record, threatened the communities of Santa Barbara, Carpinteria, Summerland and Montecito early on Thursday after destroying more than 700 homes since it began on Dec. 4, fire officials said.

“Firefighters will remain engaged in structure defense operations and scout for opportunities to establish direct perimeter control,” the California Department of Forestry and Fire Protection said in a statement, noting that the fire threatened 18,000 structures.

Gusty Santa Ana winds were forecast to whip up to 50 mph (80 kph) early in the morning and peak during the day before decreasing by evening, while warm temperatures and single-digit relative humidity persist, the National Weather Service said in an advisory.

The weather conditions will “contribute to extreme fire behavior. Any fires that develop will likely spread rapidly,” the weather service said in an advisory.

The Thomas Fire has traveled 27 miles (43 km), blackening more than 371 square miles (953 square km) in Ventura and Santa Barbara counties, an area larger than New York City.

The conflagration has destroyed 709 single-family homes, damaged 164 others and displaced more than 94,000 people. It was 30 percent contained as of Wednesday evening.

Many public schools in the Santa Barbara area canceled classes this week and will not reopen until the annual winter break is completed in January.

Some of the other fires burning over the past week in San Diego and Los Angeles counties have been largely brought under control.

Investigators determined that the Skirball Fire, which destroyed six homes in Los Angeles’ wealthy Bel-Air neighborhood and scorched a building at a winery owned by billionaire media mogul Rupert Murdoch, was started by a cooking fire at a homeless encampment, authorities said on Tuesday.

The Lilac Fire, which burned more than 4,000 acres (1,620 hectares) in northern San Diego County and destroyed 157 structures, was 96 percent contained by Wednesday, Cal Fire said.

(Additional reporting by Brendan O’Brien in Milwaukee; Editing by Hugh Lawson)