(CNN) -- A Southern California wildfire is burning uncontrollably a day after it ignited, scorching more than 31,000 acres.
In less than two days, the massive blaze has engulfed an area larger than the size of San Francisco.
The brush fire, coined Blue Cut, was 4% contained as of Wednesday evening, according to Cal Fire spokesman Daniel Berlant.
Authorities have warned more than 82,000 residents in San Bernardino County to evacuate from the fast-moving fire that began Tuesday. Some 34,500 homes are in the evacuation area.
Weather conditions and the dryness of the brush have made the fire unpredictable.
"In my 40 years of fighting fires I have never seen a fire behavior so extreme as it was yesterday," Mike Wakoski, a commander with the incident team, told reporters.
The majority of Tuesday's firefighting actions were "defensive" measures aimed at protecting structure damage, Wakoski said.
Michael Eberle, a resident of the affected area, said his family packed everything they needed to survive outside of the house, including a folder of important papers in preparation for their evacuation.
Most of the family photos are digitally stored so their main priority now is to get the family pets to safety.
They will be heading north to Phelan, California, and plan to stay with family there unless the winds shift and force evacuations there as well.
Jenny Cruz, a resident of Phelan, said her family had not been told to evacuate yet but said she thinks it's likely. She spotted at least five firetrucks setting up at the end of her street Wednesday morning and said she could see fire in the distance from her window.
"I realized the fire was starting to get really bad when it became hard to breathe when I walked outside. And when our rooms in the house started to smell like smoke. And you can see the thick black smoke outside and over our house with ashes falling down," she said.
More than 1,500 personnel and 26 crews responded to the blaze, and 178 engines, 10 air tankers and 17 helicopters have been used, according to the San Bernardino National Forest.
The massive fire about 70 miles east of Los Angeles is affecting Cajon Pass, Lytle Creek, Wrightwood, Oak Hills and surrounding areas. It has prompted Gov. Jerry Brown to declare a state of emergency in the area.
"This is a very quickly growing wildfire," a San Bernardino National Forest statement said, urging residents to follow evacuation instructions.
Fire authorities warn of "imminent threat to public safety, rail traffic and structures" in the affected areas.
The blaze started about 10:30 a.m. Tuesday in Cajon Pass, a mountain pass between the San Bernardino Mountains and San Gabriel Mountains. The size of the fire is roughly 40 square miles.
On Tuesday, six firefighters were trapped by the wildfire but found shelter at a nearby structure, according to the San Bernardino County Fire Department. Two suffered minor injuries but later returned to the fire line.
The fire quickly scorched up the dry hills as winds carried the embers. It fed on the thick, parched brush, and engulfed an unknown number of homes and structures, according to fire officials.
One resident told CNN affiliate KABC-TV in Los Angeles about the flames surrounding her house.
"We had to keep the windows up because we couldn't breathe. The smoke was so thick, and as soon as the smoke cleared, we could see that everything was gone," said Crystal Armstrong, who lost her home.
Firefighters implored residents to evacuate, saying that refusing to do so puts lives at risk.
Aerial views showed the mountains covered in plumes of smoke.
Drought-stricken California has been hit with waves of wildfires this summer, fueled by dry conditions, heat and dead brush.
Before the Blue Cut Fire, 8,000 firefighters had already been battling eight large wildfires across the state.
"One of the things we are seeing is that the fires are burning in an unprecedented fashion," Cal Fire Unit Chief Glenn Barley told reporters in Wednesday's press conference. "It's to the point where explosive fire growth is the new normal this year."