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Flames have swept over areas close to homes and roads in drought-parched San Diego County, destroying more than 10,000 acres (4,047 hectares) and filling the sky with black smoke. California Governor Jerry Brown has declared a state of emergency to free up resources.
Wind gusts were about half as intense on Thursday as the day before, which saw so-called 'firenadoes' - twisting wind columns that throw off embers - said Cal Fire spokeswoman Lynne Tolmachoff.
"That's an improvement over yesterday, and if that weather pattern persists that would be good for the firefighters," she said, adding that lower winds make it easier to put aircraft to work combating the blazes.
The blaze comes as California enters its peak fire season in the midst of one of its worst droughts in decades, setting the stage for what state officials worry could be a particularly intense and dangerous year.
A fire that erupted on Wednesday in the area of San Marcos, a community 30 miles (48 km) north of San Diego, prompted officials to issue evacuation notices for thousands of residents and students at a local California State University campus.
Officials say the blaze, which has ranged across about 800 acres (324 hectares) in steep terrain, is the top threat in the county and is only 5 percent contained. No major injuries were reported.
"As you stand here today, you can tell it's extremely hot, it's dry, we're in early May, we have a long fire season ahead," Cal-Fire Battalion Chief Nick Schuler told reporters.
The fire near San Marcos has destroyed at least three buildings, officials said.
Another blaze that broke out on the Camp Pendleton Marine Base north of San Diego had charred some 6,000 acres (2,430 hectares) by Thursday.
The San Diego Unified School district and other districts canceled Thursday classes.
Officials in the coastal city of Carlsbad said on Thursday a 400-acre (162-hectare) fire in that area was about 60 percent contained and they lifted some evacuation orders. The blaze has destroyed 18 apartment units, four houses and two commercial buildings, the city said on its website.