GUINDA (CBS SF/AP) — Firefighters concentrated their battle against the massive County Fire Wednesday on its canyon-filled northern boundary as the blaze grew to 86,000 acres by Wednesday evening.

The blaze was at 27 percent containment as of 10 p.m. Wednesday.

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Cal Fire officials said they were successful in gaining a larger foothold on the southern boundary of the blaze overnight by using fire to fight fire. Several backfires were lit that slowed the advance.

By late Wednesday afternoon, fire officials announced that they were lifting some mandatory evacuations and evacuation advisories in Yolo County. The affected areas were East of the Yolo/Napa County Line to State Highway 16 and South of County Road 53 to State Highway 128.

While others in Northern California celebrated the Fourth of July, firefighters at the base camp were serenaded by a stirring rendition of the National Anthem before they headed out to fight the fire.

Fire spokesman Israel Pinzon said Wednesday was expected to be the coolest day of the week, with temperatures 10 to 15 degrees lower than the triple digits that firefighters have faced.

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Anthony Brown, a spokesman with the California Department of Forestry and Fire Protection, said firefighters even took advantage of improving weather conditions on Tuesday to make progress in containing the fire that has now grown almost to size of San Francisco and the Peninsula.

“The weather is better than what we had over the weekend,” he said. “But it’s still hampering our efforts and it’s an area of concern.”

Nearby grape growers and wine markers say they don’t know what the impact of the heavy smoke will have on this year’s vintage.

“As long as the vineyard doesn’t burn, the next critical issue is the smoke,” said Chris Turkovich of the Turkovich Family Winery. “We ultimately don’t know what we have until its in the winery in the tanks.”

The fire was first reported around 2:00 p.m. Saturday afternoon and almost from the start triggered evacuations that have continued to grow to now include Berryessa Highlands, Markley Cove Resort and Pleasure Cove Resort neighborhoods in Napa County, as well as parts of Yolo County.

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