SAN FRANCISCO (AP) — Firefighters were warily watching for “violent” winds expected in California’s wine country Thursday that could fan the flames of a massive blaze that has destroyed nearly 250 buildings and is threatening thousands more in a small town known for hot springs, mud baths and wineries.

More fire crews and equipment were deployed overnight in and around Calistoga, a town of 5,000 people about 70 miles (110 kilometers) north of San Francisco in the hills of Napa County, after a forecast called for strong winds amid extreme heat and low humidity forecast for later Thursday.

READ MORE: Sacramento Police Officer Alexa Palubicki Accused Of Filing False Police Reports

“Fire crews are working to make as much progress on the fire as possible before anticipated winds arrive,” Calistoga officials said in a statement.

More than 2,000 firefighters are battling the Glass Fire, which has charred 89 square miles (230 square kilometers) in Napa and Sonoma counties with almost no containment. It has destroyed about 250 buildings, including 143 homes.

It’s the fourth major fire there in three years and comes ahead of the third anniversary of an Oct. 8, 2017 wildfire that killed 22 people. Three fires, driven by gusty winds and high temperatures, merged into one on Sunday, tearing into vineyards and mountain areas, including part of the city of Santa Rosa. About 70,000 people were under evacuation orders, including the entire population of Calistoga.

Red flag warnings of extreme fire danger were to continue into Friday evening for large swaths of Northern California.

Numerous studies have linked bigger wildfires in America to climate change from the burning of coal, oil and gas. Scientists say climate change has made California much drier, meaning trees and other plants are more flammable.

READ MORE: Sacramento Woman Fights For Tougher Drug Laws Aimed At Dealers After Brother's Overdose

California’s power grid operator called for voluntary conservation of electricity Thursday from 3 p.m. to 10 p.m. as high heat is expected to grip the state, taxing electricity supplies, primarily from the use of air conditioning.

About 150 miles (240 kilometers) to the north of wine country, the Zogg Fire, which also erupted during Sunday’s high winds and grew quickly, has killed four people.

The Shasta County sheriff’s office released two of their names Thursday: Karin King, 79, who was found on the road where the fire started, and Kenneth Vossen, 52, who suffered serious burns and later died in a hospital. Both were from the small town of Igo.

The deadly blaze that spread to neighboring Tehama County has burned 86 square miles (223 square kilometers) and destroyed 147 buildings, about half of them homes. It was 25% contained.

The Glass and Zogg fires are among nearly 30 wildfires burning in California. Fire-related deaths in California this year total 30.

MORE NEWS: Woman Walking On I-80 Fatally Struck By 3 Cars, North Sacramento CHP Says

Since the beginning of the year, thousands of wildfires have burned over 6,000 square miles (15,500 square kilometers) in California. More than 96,000 residents are under evacuation orders across the state, the California Department of Forestry and Fire Protection said.