Around 100 homes and other structures have been destroyed in a Northern California wildfire that put thousands of people under evacuation orders.

Fire officials said improved weather conditions helped slow the Mill Fire, which is burning 250 miles north of San Francisco.

The fire began on Friday afternoon near the city of Weed.

At least two people were injured in the fire, one of three major blazes that forced large-scale evacuations in recent days as California swelters under a heat wave expected to last through until Monday.

California is in a deep drought as it heads into what is traditionally the worst of the fire season.

Cal Fire Siskiyou Unit chief Phil Anzo said crews worked all day and night to protect structures in Weed and in a subdivision to the east known as Carrick Addition.

“There’s a lot at stake on that Mill Fire,” he said. “There’s a lot of communities, a lot of homes there.”

Weather conditions improved overnight and firefighters were able to get 20% containment, but another blaze, the Mountain Fire, that broke out on Friday north-west of Weed grew substantially.

No injuries or buildings had been reported lost in that fire. The causes for both fires are under investigation.

Mr Anzo estimated about 100 homes and other buildings were lost in the Mill Fire.

Governor Gavin Newsom declared a state of emergency for Siskiyou County and said a federal grant had been received “to help ensure the availability of vital resources to suppress the fire”.

Scientists say climate change has made the US west warmer and drier over the last three decades and will continue to make weather more extreme and wildfires more frequent and destructive.

In the last five years, California has experienced the largest and most destructive fires in state history. Weed has seen three major fires since 2014.