Six large new wildfires have erupted in the US, pushing the number of major active blazes nationwide to over 100, with more expected to break out sparked by lightning strikes on bone-dry terrain.

More than 30,000 personnel, including firefighters from across the US and nearly 140 from Australia and New Zealand, were battling the blazes that have consumed more than 648,000 hectares, according to the National Interagency Coordination Center.

“We are expecting that there will be more fire-starts today,” Jeremy Grams, lead forecaster with the National Weather Service’s Storm Prediction Center in Oklahoma, said in an interview on Saturday.

He said dry thunderstorms, which produce lightning but little rain, are expected for parts of the Rocky Mountain region, while the US northwest has critical fire weather conditions that include strong winds and low relative humidity.

Firefighters were battling another day of extremely hot temperatures and strong winds on Saturday, the National Interagency Coordination Center said.

The fires have scorched states from Washington to New Mexico, with California among the hardest hit.

A mechanic helping to fight the Carr Fire near Redding in northern California was killed in a car crash on Thursday, the eighth person to die in that conflagration.

The 77,243-hectare Carr Fire has destroyed nearly 1100 homes.

About 160km southwest of the Carr Fire, about 3,500 firefighters are battling the Mendocino Complex Fire, which has burned 132,828 hectares as of Saturday and was the largest fire on record in California.