MAPS: A look at the 'County Fire' in Yolo County
More than 1,000 firefighters are still battling the blaze that nearly doubled in size on Monday.
Most of the action Wednesday will happen around the small town of Guinda, on State Highway 16, which lies near the eastern side of the fire.
PHOTOS: County Fire burning near Lake Berryessa
"The fire laid down last night," said Cal Fire spokesman Israel Pinzon. Crews worked all night building containment lines along the fire.
The huge blaze was choking skies with ash and smoke, prompting some officials to cancel Fourth of July fireworks shows and urge people to stay indoors to protect themselves from the unhealthy air.
At least 2,500 people have been told to evacuate as the so-called County Fire continues to spread, said Anthony Brown, a spokesman with the California Department of Forestry and Fire Protection.
Brown said the blaze started Saturday and is surging through rugged terrain northwest of Sacramento amid hot and dry weather. "The weather is better than what we had last weekend. But it's still hampering our efforts and it's an area of concern," he said.
So far this year, wildfires have burned 4,200 square miles in the United States, according to the fire center. That's a bit below last year's acreage to date -- which included the beginning of California's devastating fire season -- but above the 10-year average of 3,600 square miles.
Because of the Independence Day holiday, authorities are also concerned about the possibility of campfires or fireworks starting new fires because of the dry, hot conditions.
Cal Fire officials say their goal is to have full containment of this fire by next Tuesday, July 10.
The fire sent smoke across the Bay Area, as far west as Petaluma and as far south as San Francisco and Redwood City, according to the National Weather Service in San Francisco.
CAL FIRE map of the "County Fire"
The Associated Press contributed to this story.