PORTLAND, Ore. >> The nation’s largest wildfire torched more dry forest in Oregon and forced the evacuation of a wildlife research station today as firefighters had to retreat from the flames for the ninth consecutive day due to erratic and dangerous fire behavior.

Firefighters were forced to pull back as flames, pushed by winds and fueled by bone-dry conditions, jumped fire-retardant containment lines and pushed up to 4 miles into new territory, authorities said.

The destructive Bootleg Fire in south-central Oregon is just north of the California border and grew to more than 476 square miles, an area about the size of Los Angeles.

Fire crews were also rushing to corral multiple “slop fires” — patches of flames that escaped fire lines meant to contain the blaze — before they grew in size. One of those smaller fires was already nearly 4 square miles in size. Thunderstorms with dry lightning were possible today as well, heightening the dangers.

“We are running firefighting operations through the day and all through the night,” said Joe Hessel, incident commander. “This fire is a real challenge, and we are looking at sustained battle for the foreseeable future.”

Today, the fire reached the southern edge of Sycan Marsh, a privately owned wetland that hosts thousands of migrating birds and is a key research station on wetland restoration.

The blaze, which was 25% contained, has burned at least 67 homes and 100 buildings while threatening thousands more in a remote landscape of forests, lakes and wildlife refuges.

At the other end of the state, a fire in the mountains of northeast Oregon grew to nearly 19 square miles.

The Elbow Creek Fire that started Thursday has prompted evacuations in several small, rural communities around the Grande Ronde River about 30 miles (50 kilometers) southeast of Walla Walla, Washington. It was 10% contained.

Natural features of the area act like a funnel for wind, feeding the flames and making them unpredictable, officials said.

In California, a growing wildfire south of Lake Tahoe jumped a highway, prompting more evacuation orders, the closure of the Pacific Crest Trail and the cancellation of an extreme bike ride through the Sierra Nevada.

The Tamarack Fire, which was sparked by lightning on July 4, had charred about 36 square miles (93 square kilometers) of dry brush and timber as of today. Crews were improving a line protecting Markleeville, a small town close to the California-Nevada state line. It has destroyed at least two structures, authorities said.

About 500 fire personnel were battling the flames Sunday, “focusing on preserving life and property with point protection of structures and putting in containment lines where possible,” the U.S. Forest Service said.

Meteorologists predicted critically dangerous fire weather with lightning possible through at least today in both California and southern Oregon.

“With the very dry fuels, any thunderstorm has the potential to ignite new fire starts,” the National Weather Service in Sacramento, California, said on Twitter.

Extremely dry conditions and heat waves tied to climate change have swept the region, making wildfires harder to fight. Climate change has made the West much warmer and drier in the past 30 years and will continue to make weather more extreme and wildfires more frequent and destructive.

Firefighters said in July they were facing conditions more typical of late summer or fall.

Northern California’s Dixie Fire roared to new life Sunday, prompting new evacuation orders in rural communities near the Feather River Canyon. The wildfire, near the 2018 site of the deadliest U.S. blaze in recent memory, was 15% contained and covered 39 square miles. The fire is northeast of the town of Paradise, California, and survivors of that horrific fire that killed 85 people watched warily as the new blaze burned.

Pacific Gas & Electric equipment may have been involved in the start of the Dixie Fire, the nation’s largest utility reported to California regulators.

PG&E said in a report Sunday to the California Public Utilities Commission that a repair man responding to a circuit outage on July 13 spotted blown fuses in a conductor atop a pole, a tree leaning into the conductor and fire at the base of the tree.

The Dixie Fire has grown to nearly 47 square miles (122 square kilometers), largely in remote wilderness. The utility said investigators with the California Department of Forestry and Fire Protection have collected equipment from the location.

PG&E equipment has repeatedly been linked to major wildfires, including a 2018 fire that ravaged the town of Paradise and killed 85 people.

At least 16 major fires were burning in the Pacific Northwest alone, according to the Forest Service.