LOS ANGELES (Reuters) - Firefighters battling a wildfire about 40 miles (64 km) north of Los Angeles faced another day of brutal heat on Tuesday after reporting progress containing the blaze under cooler conditions overnight.

About 300 miles further north in drought-hit California, another fire ravaged a hilly area near the scenic coastal town of Carmel-by-the-Sea, churning through 16,100 acres (6,500 hectares) and destroying 20 homes, authorities said.

About 3,000 firefighters have been struggling to control the so-called Sand Fire in a 59-square-mile (153 sq km) area on the northwestern fringes of the Angeles National Forest since Friday.

The fire was 25 percent contained on Tuesday morning, up from just 10 percent on Monday evening, as crews backed by bulldozers hacked out buffer lines around the blaze, authorities said.

But firefighters on Tuesday afternoon will be laboring in above average heat of 102 degrees Fahrenheit (39 degrees Celsius) and low humidity, National Weather Service specialist Stuart Seto said.

Like wind and exceptionally dry conditions, low humidity hampers firefighting efforts.

One person was found dead over the weekend in a fire-gutted vehicle parked in a driveway and the blaze has destroyed at least 18 homes.

No other deaths or serious injuries have been reported so far, however. As many as 30,000 people had been forced to evacuate their homes due to fire, but officials gave the all-clear for most residents to return late on Monday.

An air quality advisory remained in effect until midnight on Tuesday midnight, as acrid layers of smoke continued to drift across a widespread area.

Among properties damaged by flames was the landmark Sable Ranch, a popular location for television and movie shoots.

Further north, the so-called Soberanes Fire, burning in the Los Padres National Forest in Monterey County, threatened 1,650 structures by Monday evening and was only 10 percent contained, the U.S. Forest Service said.

The causes of both fires are still under investigation, but they are among some 3,750 blazes large and small to have erupted across California since January. The higher-than-normal total has collectively scorched more than 200,000 acres (80,940 hectares), state fire officials said.

The biggest so far was last month's Erskine Fire, which consumed 48,000 acres (19,429 hectares) northeast of Bakersfield, killing two people and destroying about 250 structures.

By comparison, the 2003 Cedar Fire ranks as the biggest on record in the state, burning more than 273,000 acres (110,480 hectares) and killing 15 people.

(Reporting by Alex Dobuzinskis in Los Angeles and Brendan O'Brien in Milwaukee; Editing by Raissa Kasolowsky and Tom Brown)