The carnage caused by the wildfires sweeping northern California continued to grow more than a week after the blaze ignited, as the number of people missing leaped to more than 600 and air quality across the region ranked among the worst anywhere in the world.  The blaze north of Sacramento, dubbed the Camp Fire, has already become California’s deadliest, claiming 63 lives.

Thousands of people have been left homeless as the fire swept through Paradise and adjacent towns in Butte County, destroying 9,700 buildings. Authorities said on Friday morning that the fire had expanded to more than 140,000 acres and was still only 45 percent contained. Tens of thousands of people have been evacuated and now millions more are dealing with poor air quality that has darkened California’s blue skies. California governor Jerry Brown has warned the situation reflected a “new abnormal” for the state as hotter temperatures and drier conditions combined to make wildfires a near-constant threat.

The number of people missing in the fire-ravaged area was raised to 631 by the county sheriff’s office, a sharp increase over earlier estimates. This weekend, President Donald Trump will visit Butte County as well as southern California’s Woolsey fire, which killed three people, destroyed hundreds of buildings and is now 69 per cent contained.  Smoke from the fires has been drifting over the capital city of Sacramento and more than 100 miles south to the San Francisco Bay area, shutting down businesses and schools, prompting public health warnings and sending residents in search of face masks and air purifiers.

The air quality index in Sacramento exceeded the 300-point threshold generally considered to be “hazardous” or “emergency conditions” on Thursday and Friday, according to the US Environmental Protection Agency.  In San Francisco, readings neared 300 on Thursday and remained above 200 on Friday. The Department of Public Health said the city was experiencing “unusually smoky air” as a result of local weather patterns and warned residents to “stay indoors and avoid exposure to the outside air”.