Fire crews made significant progress overnight against a wildfire burning for nearly a week in Southern California coastal mountains, officials said Sunday.

More than 1,600 firefighters were battling the blaze in the Santa Ynez Mountains west of Santa Barbara on land and by air. They were able to stop its forward growth, and the blaze was 78% contained, federal officials said.

The Alisal Fire started last Monday and has scorched nearly 27 square miles (69 square kilometers). It is threatening about 400 structures.

A 1 1/2-acre (0.6 hectare) spot fire that ignited outside a retardant line on the blaze’s northwestern corner was quickly contained by firefighters who used bulldozer and hand lines on the ground and doused the flames with water from the air. On Sunday, few hot spots remained, and fire crews were focused on increasing containment.

Cooler temperatures were forecast for Sunday, but winds with gusts around 20 mph (32 kph) were still expected in the area, officials said.

The fire erupted during fierce winds last week and spread rapidly down the face of the mountain range, leaping a highway and railroad to the beach below. Firefighting weather greatly improved since then, allowing airplanes and helicopters to bombard the fire with retardant and water.

California wildfires have scorched nearly 3,900 square miles (10,101 square kilometers) this year and destroyed more than 3,600 homes, businesses and other structures, according to the state Department of Forestry and Fire Protection.

A historic drought in the American West tied to climate change is making wildfires harder to fight. It has killed millions of trees in California alone. Scientists say climate change has made the West much warmer and drier in the past 30 years and will continue to make weather more extreme and wildfires more frequent and destructive.