Walls of flames are quickly ripping the Northern California city of Redding, where an "out of control" fire has killed one person and is forcing thousands of residents out of their homes.

The Carr Fire in Shasta County grew rapidly Thursday night, ravaging several small communities as it began burning into Redding, a city of about 95,000 people around 190 kilometres south of the California-Oregon border.

“This fire is extremely dangerous and is moving with no regard to what's on its path,” Cal Fire Incident Commander Chief Brett Gouvea told reporters.

A private hire bulldozer operator died Thursday while battling the fire but no more details have been released.

The operator, who has not been identified, is the state's second fire-related death in recent weeks. Braden Varney, 36, a heavy fire equipment operator, was killed while batting another blaze near Yosemite National Park.

“As we mourn the loss, we also battle a fire that is moving extremely quickly and erratically into western Redding,” Gouvea said.

More than 1,700 firefighters have been trying to control the blaze since it broke out Monday but hot and windy conditions continue fuelling it, officials said. The California National Guard is helping with the firefight, Cal Fire spokesman Scott McLean told CNN.

The fire has destroyed 15 structures and is threatening at least 500 more as it continues it's rapid rate and erratic behaviour.

“The fire is creating a huge wind vacuum and moving very rapidly toward west Redding. This fire is out of control!,” the California Highway Patrol said in a Facebook post Thursday night urging residents to evacuate.

At least five babies are being evacuated from the neonatal intensive care unit at Mercy Medical Center due to the fire, hospital spokesman Rick Plummer said.

While the hospital is not under a mandatory evacuation order, the infants are being evacuated because of the time and intense resources needed to relocate them.

Medics and hospital staff have been directly impacted by the fire.

“Several staff members have evacuated their own homes then returned to care for patients” Plummer said. Several members have lost their homes.”

Hospital staff are preparing to evacuate the entire facility if needed, a Cal Fire spokesman said.

California Gov. Jerry Brown had declared a state of emergency for Riverside and Shasta counties on Thursday in response to the fire.

The Carr Fire is among 88 active large fires scorching the country and one of six large wildfires in California, the National Interagency Fire Center said.