CALIFORINA — Fire crews in California and Oregon battled the largest active wildfires in their respective states this year as thousands of residents were under evacuation orders, while smoke from the blazes triggered health alerts across the western United States.
In California, the Park Fire exploded to become the state's largest wildfire of the year in 24 hours on Thursday, Xinhua news agency reported.
The blaze, which started Wednesday afternoon near Chico in Butte County, grew dramatically overnight, fueled by winds and dry conditions.
The fire burned 45,550 acres (184.3 sq km), and only 3 per cent had been contained as of Thursday noon, according to the latest update of the California Department of Forestry and Fire Protection (Cal Fire).
No injuries have been reported.
Evacuations were ordered in Butte and Tehama counties as temperatures exceeded 100 degrees Fahrenheit (37.8 degrees Celsius), and high winds continued to drive the fire's expansion.
A suspect was arrested on suspicion of starting the Park Fire. Butte County District Attorney Mike Ramsey said in a release that the 42-year-old man was taken into custody early on Thursday.
Witnesses reported seeing someone pushing a burning car into a gully in Bidwell Park shortly before the fire ignited. The vehicle tumbled 60 feet (18.3 metres) down an embankment and burned completely, sparking the massive blaze, according to the release.
In eastern Oregon, firefighters were still battling the Durkee Fire on Thursday, one of the largest active wildfires in the United States.
The lightning-sparked fire has scorched nearly 270,000 acres (1,092.7 sq km) since it began on July 17 near the Oregon-Idaho border. Amid high temperatures, extremely dry vegetation and strong winds, the fire was not contained as of Thursday morning.
The Durkee Fire has already injured three people and destroyed two homes as well as 12 other structures, according to the Oregon Department of Emergency Management. Evacuation orders were in place for areas around the fire.
Dense smoke from the flames periodically forced the closure of Interstate 84 freeway, impacting travel in the region.
Oregon has been hit hard by wildfires in recent days as more than 30 fires, including the Durkee Fire, are currently burning across the state. Oregon Governor Tina Kotek has deployed National Guard resources to assist with firefighting efforts.
Extreme fire behaviour was observed in the Durkee Fire, including the formation of "pyrocumulus clouds" -- a sign that the fire was creating its own weather system and was especially challenging to control.
Weather conditions continued to pose significant challenges for firefighters. The National Weather Service in Boise reported on Thursday that there were over 2,800 cloud-to-ground lightning strikes across southeast Oregon and Idaho on Wednesday alone, raising concerns about potential new fire starts.
The wildfires were triggering air quality alerts across the western parts of the United States, as smoke drifted from California to Oregon, Idaho, and other states.
Air quality alerts have been issued for parts of Colorado, Idaho, Oregon, and Washington as residents grapple with the health impacts of widespread smoke. Officials were urging residents to stay informed about evacuation orders and air quality advisories.
Climate scientists pointed to climate change as a factor in the increasing frequency of wildfires, particularly those sparked by lightning, across the Pacific Northwest.
The region has endured record-breaking heat, with record-breaking temperatures and persistently dry conditions creating an environment conducive to rapid fire spread.