A wildfire burning north of Napa exploded overnight to 12,000 acres, touching and nearly merging Tuesday with the southern edge of the massive Rocky fire.
The rapidly growing Jerusalem fire that started Sunday is threatening 50 homes, prompting mandatory evacuations for residents living near approaching flames.
The fire is burning northeast of Middletown in the Jerusalem Valley area, where erratic winds contributed to intense fire activity, according to the California Department of Forestry and Fire Protection.
"Our hope is that it's not going to burn further north," Cal Fire spokesman Daniel Berlant said.
Firefighters are concerned that as the fire continues to burn to the east, it will consume thousands of acres of open land and dry brush, he said.
Although the Lake County fire grew 6,000 acres overnight, Cal Fire says the burning conditions slowed due to increasing humidity and cooler temperatures. More than 1,100 firefighters, however, are continuing an aggressive attack on the blaze.
A new fire map released Tuesday shows the Jerusalem fire touching the southernmost edge of the 69,636-acre Rocky fire, which is 88% contained.
The causes of both fires are under investigation.
Berlant said there were nearly 250 wildfires in the past week.
The Rocky and Jerusalem fires are two of 18 wildfires burning in California, mostly in the northern part of the state. More than 10,000 firefighters are battling blazes and are receiving aid from Arizona, Nevada and New Mexico.
For breaking news in California, follow @VeronicaRochaLA.