Fire crews made progress in the battle against major wildfires that have left a trail of damage in the western United States, but thousands of firefighters continue to tackle the flames.
In northern California, the Park fire grew at ferocious speeds to become one of the largest wildfires in the state this year. In southern California, a blaze swept through the historic mining town of Havilah. And in Oregon and Idaho, authorities were assessing the damage caused by several large wildfires raging there.
Acres burned
US wildfires are measured in terms of acres. While the size of a wildfire doesn’t necessarily correlate to its destructive impact, acreage provides a way to understand a fire’s footprint and how quickly it has grown.
There are 2.47 acres in a hectare, and 640 acres in a square mile, but this can be hard to visualise. Here are some easy comparisons: one acre equates to roughly the size of an American football field. London’s Heathrow airport is about 3,000 acres. Manhattan covers roughly 14,600 acres, while Chicago is roughly 150,000 acres, and Los Angeles is roughly 320,000 acres.
Megafire
A megafire is defined by the National Interagency Fire Center as a wildfire that has burned more than 100,000 acres (40,000 hectares). That’s an area about the size of Rhode Island.
Containment level
A wildfire’s containment level indicates how much progress firefighters have made in controlling the fire. Containment is achieved by creating perimeters the fire can’t move across. This is done through methods such as putting fire retardants on the ground, digging trenches, or removing brush and other flammable fuels.
Containment is measured in terms of the percentage of the fire that has been surrounded by these control lines. A wildfire with a low containment level, such as 0% or 5%, is essentially burning out of control. A fire with a high level of containment, such as 90%, isn’t necessarily extinguished but rather has a large protective perimeter and a rate of growth that is under control.
Evacuation orders and warnings
Evacuation warnings and orders are issued by officials when a wildfire is causing imminent danger to people’s life and property. According to the California office of emergency services, an evacuation warning means that it's a good idea to leave an area or get ready to leave soon. An evacuation order means that you should leave the area immediately.
Red flag warning
A red flag warning is a type of forecast issued by the National Weather Service that indicates when weather conditions are likely to spark or spread wildfires. These conditions typically include dryness, low humidity, high winds and heat.
Prescribed burn
A prescribed burn, or a controlled burn, is a fire that is intentionally set under carefully managed conditions in order to improve the health of a landscape. Prescribed burns are carried out by trained experts such as members of the US forest service and indigenous fire practitioners. Prescribed burns help remove flammable vegetation and reduce the risk of larger, more catastrophic blazes, among other benefits.
Prescribed burning was once a common tool among Native American tribes who used “good fire” to improve the land, but was limited for much of the last century by a US government approach based on fire suppression. In recent years, US land managers have returned to embracing the benefits of prescribed burns, and now conduct thousands across the country every year.
The fires are some of more than 100 blazes burning in the US at the moment. Some were lit, but many were sparked by the weather, with climate change increasing the frequency of lightning strikes as the western US endures blistering heat and bone-dry conditions.
As of Monday, the Park fire had scorched an area greater than the city of Los Angeles, darkening the sky with smoke and engaging thousands of firefighters. The blaze spanned more than 360,000 acres near the university town of Chico.
The fire started on Wednesday, when authorities say a man pushed a burning car into a gully in Chico and then fled. The man accused of setting the fire made his first appearance in court on Monday and was charged with felony arson of an inhabited structure or property.
Officials did not expect the fire to move farther into Chico, and over the next three days, crews plan to extinguish hot spots and remove hazards, said Jeremy Pierce, Cal Fire operations section chief, on Sunday. Firefighters increased containment to 12% on Monday, aided by cooler temperatures and more humidity, officials said.
The fire over the weekend encroached on Paradise, the town that in 2018 lost 85 people to a ferocious wildfire. Paradise and several other Butte county communities were under an evacuation warning on Sunday. Yet the fire’s southernmost front, which is closest to Paradise, was “looking really good”, Pierce said.
Winds and temperatures were expected to increase slightly amid a drop in humidity, officials said in an update early Monday.
Nearly 4,000 firefighters are battling the fire, aided by numerous helicopters and air tankers. Reinforcements are expected to give much-needed rest to local firefighters, some of whom have been working nonstop since Wednesday, said Jay Tracy, a Park fire headquarters spokesperson.
“This fire is surprising a lot of people with its explosive growth,” he said. “It is kind of unparalleled.”
In southern California, about 2,000 people were ordered to evacuate because of a fire sweeping through the Sequoia national forest. The wind-driven blaze, known as the Borel fire, was fed by dried, dead plants and moved fast and had eaten up more than 53,000 acres by Monday.
No fatalities have been reported in the Park and Borel fires, but some people were increasing the danger for everyone by disregarding evacuation orders, said Andrew Freeborn of the Kern county fire department.
“When people are trying to ignore the orders and later call for rescue, that takes firefighters away from the task of fighting the fires,” he said. “This fire is moving at a pace and with such intensity that individuals should not be thinking they can wait until the last minute. They need to get out of the way.”
The historic mining town of Havilah and several other communities were “heavily impacted” by the fires, but it was too soon to count the burned homes, Freeborn said.
Although cooler-than-average temperatures are expected through the middle of this week, that does not mean existing fires will disappear, said Marc Chenard, a meteorologist at the National Weather Service’s weather prediction center in College Park, Maryland.
The National Weather Service issued “red flag” warnings on Monday for wide swaths of Idaho, Montana, Utah and Wyoming, in addition to parts of California, meaning dry fuels and stronger winds were increasing the fire danger, the weather service said.
Fires burned across eastern Oregon and eastern Idaho, where officials were assessing damage from a group of blazes called the Gwen fire, which was estimated at 43 sq miles (111 sq km) as of Sunday.
