The fire 50 miles north-west of Los Angeles mushroomed to 43 square miles on Friday as 900 firefighters used engines, aircraft, bulldozers and other equipment to battle the flames.
But it was hoped that an expected change in the weather over the weekend would give fire much-needed assistance.
Forecasters said a weekend of increased humidity should help teams fighting the early-season blaze make some gains.
Despite its size and speed of growth, the fire that broke out on Thursday and quickly moved through the Camarillo Springs area has caused damage to just 15 buildings. It is, however, threatening 2,000 homes.
The type of blaze that hit the area does not usually strike Southern California wild-land until September or October, after the summer has dried out hillside vegetation. But the state has seen a severe drought during the past year, with the water content of California’s snowpack only 17 per cent of its normal level.
That created late-summer conditions by May, and when hot winds and high temperatures arrived last week, the spring flames that firefighters routinely knock down once or twice a year quickly roared up a hillside.
On Friday, the wildfire stormed back through canyons toward inland neighborhoods when winds reversed direction. The blaze is one of more than 680 wildfires in the state so far this year – about 200 more than average.