Wind-driven walls of flame have prompted mass evacuations in Southern California and badly injured two firefighters as hundreds of thousands of residents endured a second day of power shut-offs meant to counter heightened fire risks from gusty, dry weather.

The latest threats came amid what meteorologists called the strongest onslaught of extreme winds – and lowest humidity levels – yet documented during an already epic California wildfire season ranked as the worst on record in terms of acreage burned.

Fires have scorched more than 16,500 square kilometres this year, with thousands of homes destroyed and 31 lives lost.

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Red flag warnings for incendiary weather conditions remained posted across much of California due to extreme winds producing gusts in excess of 130km/h, according to the California Department of Forestry and Fire Protection.

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No property losses were immediately reported.

But two firefighters among an estimated 500 personnel battling the flames with bulldozers and hand tools were taken to hospital with severe burns, authorities said.

The latest outbreak of fires capped a summer of record California wildfire activity stoked by increasingly frequent and prolonged bouts of extreme heat, drought, wind and dry lightning storms that scientists point to as a consequence of climate change.

-AAP