Hundreds of firefighters battled a wildfire moving from Napa County into the foothills of Solano County as cooler weather helped firefighters gain ground on the bone-dry terrain across the heart of wine country.

Kevin Colburn, a spokesman for Cal Fire, told FOX News on Monday that about 3,750 acres had burned and the blaze was about 40 percent contained.

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"Obviously if the winds pick up to what we're expecting, that's going to be a concern," Colburn told FOX News. "Right now the temperatures are cooler, and so with it being a little bit cooler today hopefully that will give us an advantage ... because we are concerned about the winds."

About 400 people remained evacuated, Colburn said.

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One fire spread across nearly 6 square miles in Napa County and moved into a mostly rural area of Solano County. It threatened more than 100 buildings as it fed on grassy woodland about 40 miles southwest of Sacramento, said Roger Archey, a spokesman for the California Department of Forestry and Fire Protection.

Elsewhere, firefighters in southern New Mexico were trying to stop a wildfire that has consumed 43,000 acres — or more than 67 square miles — of grass and brush since starting in the Lincoln National Forest, a U.S. Forest Service fire information officer said.

Two other lightning-sparked wildfires also have burned nearly 30,000 acres — or more than 46 square miles — in New Mexico, one west of Roswell in the southeastern part of the state and the other west of Raton in the north.

Wildfires have destroyed more than 175 homes in Northern California so far this year. Blazes started popping up in the region just as California's unofficial fire season began in mid-May, following the state's driest two-month period on record.

About 25 miles south of San Jose, many residents were being let back into their homes Monday after being chased out by two fires blamed on lightning that blackened a total of about 2 square miles. Officials said one fire was 90 percent contained Monday and the other 50 percent contained.

Thunderstorms were responsible for as many as 75 fires in Shasta-Trinity National Forest, about 160 miles north of Sacramento. They ranged in size from less than an acre to more than a square mile. None immediately threatened homes, said Forest Service spokesman Michael Odle.

Mendocino County had as many as 90 fires, charring a total of 5,000 acres, fire officials said.

South of San Francisco, a fire that started Friday in Santa Cruz County, destroying homes and closing a stretch of highway, was contained after charring just less than a square mile. Roughly 2,000 people fled their homes Friday.

It was the third major blaze to hit Santa Cruz County in the past month. A 520-acre blaze destroyed 11 buildings in the Santa Cruz Mountains, and a fire near Corralitos covered more than 4,200 acres and destroyed about 100 buildings.

Just south of San Francisco, residents of the small city of Brisbane were being allowed back into their homes Monday after a grass fire scorched several hundred acres.

The Associated Press contributed to this report.