Raging wildfires have wreaked havoc in California as they have burned nearly one million acres in a week and destroyed hundreds of homes as weekend weather threatened to spark new fires and overwhelm the state’s firefighting ability. Responding to the emergency, President Donald Trump issued on Saturday a major disaster declaration to provide federal assistance. Gov. Gavin Newsom said in a statement that the declaration will also help people in counties affected by the fires with crisis counselling, housing and other social services.

The fires have torched nearly 700 homes and other structures; tens of thousands of people have evacuated. More than 13,700 firefighters were on the scene. Light winds and cooler and more humid nighttime weather helped fire crews make progress on those fires. The forecast for coming days has officials worried lightning may set even more fires. Thunderstorm systems are expected to impact portions of Northern California. The National Weather Service issued a red flag warning of high fire danger across the Bay Area and along the Central Coast, beginning from Sunday morning to Monday afternoon.

Since thousands of lightning strikes began on Aug. 15, the state reported 585 wildfires that have burned nearly a million acres, or 1,562 square miles (4,046 square kilometres), according to California Department of Forestry and Fire Protection (Cal Fire).

California’s oldest state park, Big Basin Redwoods, has been damaged by the fires, which have charred hundreds of massive ancient coast redwoods – some more than 1,000 years old. Dozens of other state parks, beaches and nature reserves have also been closed.

Smoke from the fires is making the air quality in parts of California some of the worst in the world. A blanket of smoke – visible from satellite images – is covering parts of California, and the U.S. Environmental Protection Agency has listed air quality in areas across the state as “very unhealthy.”