On Wednesday, firefighters continued to extinguish smoldering fires along the Park Fire’s containment lines, keeping the flames contained to the containment area of ​​the Northern California wildfire.

According to Cal Fire, the Park Fire’s size was 429,259 acres (670 square miles) as of Wednesday morning for the second day in a row, with containment increasing from 39% to 40% in 24 hours. Most fire activity remained in the northeastern portion of the fire in Tehama County.

According to a Cal Fire situational update Wednesday morning, there was minimal fire activity overnight, with firefighters busy with cleanup and patrolling along containment lines to ensure residents can safely return to their homes.

Favorable weather conditions continued in the region, and slightly lower potential for spot fires and lower heat along containment lines was expected Wednesday, said Jan Smoots, a Cal Fire fire behavior analyst.

Cal Fire expected a slight increase in wind speeds over the region north of the Park Fire, with gusts reaching 17-22 mph over exposed ridges. However, conditions in the area were expected to calm down by the evening.

“There is a potential for a re-ignition in areas where we have ongoing fuels against your (containment) line. Be aware of that,” Smoots told firefighters in a briefing Wednesday morning. “We still have a lot of dead trees that are burning their tops and potentially creating embers that could blow across the lines.”

Cal Fire expects warm and dry afternoons for the season this week, followed by nights with moderate to good humidity to help contain potential fire activity.

Spot fires occur when airborne embers land on the unburned side of a fire line. Firefighting involves removing or extinguishing any burning or smoldering material along the fire lines.

More than 5,400 firefighters were deployed to the Park Fire on Wednesday. Cal Fire said firefighters are working to contain smoke, suppress spot fires, remove dangerous trees weakened by flames and reinforce containment lines and emergency containment lines to prevent potential flare-ups.

Wednesday’s Park Fire remained the fourth-largest wildfire in California history. The third-largest was the Mendocino Complex Fire, which began in July 2018 and burned 459,123 acres of land. The August Complex Fire, which burned 1.03 million acres across seven Northern California counties, is the largest in state history; it killed one person and destroyed 935 structures.

The wildfire has burned more than 376,000 acres in Tehama County and nearly 53,000 acres in Butte County. The wildfire has also affected areas in Plumas and Shasta counties, where some evacuation warnings remained in effect Tuesday, according to Cal Fire.

The Tehama County Sheriff’s Office announced Tuesday afternoon that evacuation zones in the foothills along the western flank of the Park Fire’s service area have been returned to “normal” status. In zones in Mineral Township, evacuation orders have been reduced to evacuation warnings.

The Park Fire, which had been raging for 21 days as of Wednesday, began on July 24 in Butte County east of Chico following a suspected act of arson.

The Park Fire is the largest arson-caused wildfire in California on record. According to Cal Fire, the wildfire destroyed 641 structures and damaged 52 others in Butte and Tehama counties. The total also includes infrastructure.

In Butte County, the fire destroyed 428 buildings and damaged 47 others. According to Cal Fire, the fire in Tehama County destroyed 213 buildings and damaged five others.