The largest wildfire in California this year has been significantly contained after the previously severe fire season in the state has at least temporarily given way to relative calm.

The Park Fire was 53 percent contained as of Monday after ravaging nearly 680 square miles (1,738 square kilometers) in several northern counties, destroying 637 structures and damaging 49, making it the fourth-largest wildfire in state history.

Much of the fire area is currently in the cleanup phase, which means extinguishing smoldering material along containment lines, and residents of evacuated areas are returning home. Wood is still burning in the northeast corner.

The fire is burning islands of vegetation within containment lines, Cal Fire’s situation summary said.

The Park Fire was reportedly started by arson in a wilderness park outside the Central Valley town of Chico on July 24. It spread northward with astonishing speed under adverse conditions, climbing the western slope of the Sierra Nevada.

July was marked by exceptional heat in most parts of California. Two consecutive wet winters left lush vegetation throughout the state drying out and becoming flammable. Wildfires broke out across the state.

According to Daniel Swain, a climate researcher at the University of California, Los Angeles, the first half of August was warmer than average, but not record-breaking.

“We are still seeing fairly regular ignitions and significant fire activity, but the pace has slowed and the magnitude of that activity, the intensity and the initial rate of spread are not as high as they once were,” he said in an online briefing on Friday.

“However, vegetation in most parts of California is drier than average and will likely remain so throughout most of California for the foreseeable future,” he said.

There are signs of a return of extreme heat in parts of the West in late August/early September, Swain said.

“I would then expect a renewed increase in wildfires in much of the West, including California,” he said.