Wildfires have whipped by powerful winds swept through California wine country, killing at least 10 people and injuring at least 100.

They have also destroyed 1500 homes and businesses and sent thousands fleeing as flames raged unchecked through high-end resorts, grocery stores and tree-lined neighbourhoods.

The fires broke out nearly simultaneously and then exploded overnight, sending residents fleeing as embers rained down and flames raged around them.

Two hospitals in Santa Rosa, the largest city in the region with 175,000 people, were forced to evacuate patients.

Later on Monday, fires from ruptured gas lines dotted the smoky landscapes of blackened Santa Rosa hillsides. Fire trucks raced by smouldering roadside landscaping in search of higher priorities.

The flames were fickle in some corners of the city. One hillside home remained unscathed while a dozen surrounding it were destroyed.

The majority of the injured were treated for smoke inhalation, according to St Joseph Health, which operates hospitals in the Santa Rosa area.

Two were in critical condition and one was in serious condition.

A house burns in Santa Rosa, California. Photo: AP

The number of injured is expected to climb as information comes in for all the other areas affected by the firestorm consuming the state.

Hundreds of homes in the Fountain Grove area were leveled by flames so hot they melted the glass off of cars and turned aluminium wheels into liquid.

One neighbourhood of older homes was scorched, leaving only brick chimneys and downed power lines.

Residents who gathered at emergency shelters and grocery stores said they were shocked by the speed and ferocity of the flames. They recalled all the possessions they had left behind and were lost.

Some of the largest of the 14 blazes burning over a 200-mile region were in Napa and Sonoma counties, home to dozens of wineries that attract tourists from around the world. They sent smoke as far south as San Francisco, about 95 kilometers away. The causes of the fires were unknown.

The fires throughout the region were among the deadliest in California history, and fire officials expected the number of fatalities to increase.

Winds have posed a challenge to firefighters in the state this year despite a relatively wet winter that followed years of drought.

October has generally been the most destructive time of year for California wildfires. What was unusual Sunday, however, was to have so many fires take off at the same time.

Flames consume a home as an out of control wildfire move through Glen Ellen, California. Photo: Getty

Governor Jerry Brown declared a state of emergency in Napa, Sonoma, Butte, Lake, Mendocino, Nevada and Yuba counties.

Authorities imposed a sunset-to-sunrise curfew in Santa Rosa, saying they were on the lookout for looters.

The ferocity of the flames forced authorities to focus primarily on getting people out safely, even if it meant abandoning structures to the fire.

Elsewhere in the state, a fire churning through canyons in hilly neighbourhoods of Orange County burned at least half a dozen homes and forced residents of about 1000 homes to evacuate.

Mr Brown also declared a state of emergency for Orange County.