Firefighters are containing California's giant wildfires thanks to a favorable turn in the weather — here are the latest updates

• At least seven people have died and thousands were evacuated due to wildfires in Northern California.
• Two of the blazes, the SCU Lightning Complex and the LNU Lightning Complex Fires, are the second and third biggest wildfires in California history.
• Better weather this week has made the fires easier to contain, Cal Fire said on Wednesday.
• Climate change is increasing the length and severity of wildfire season: Nine of California's 10 most destructive wildfires have occurred since 2000.

Nearly two weeks after almost 11,000 bolts of lightning sparked hundreds of wildfires across California, firefighters are making progress in battling the state's 20 largest blazes.

Two of those fires, the SCU Lightning Complex and the LNU Lightning Complex, have become the second- and third- biggest in California's history, after growing to nearly 369,000 acres each.

As of Wednesday morning, 625 total fires in the state had collectively spread across more than 1.6 million acres, or around 2,000 square miles — an area larger than Delaware. They've destroyed more than 2,260 structures, though officials with California's Department of Forestry and Fire Protection (Cal Fire) said the number could rise to more than 3,000 once they're able to inspect burned regions more thoroughly.

However, Cal Fire said "favorable weather conditions," including cooler, wetter air and a respite from lightning and wind, have allowed firefighters to make considerable progress. The two biggest blazes are more than 33% contained, and several other major fires are at more than 50% containment.

"The threat of lightning and gusty and erratic winds that accompany thunderstorms passed, so that is going to be good news for the firefighters out there," meteorologist Cindy Palmer told The Mercury News on Monday.

At least seven people have died in the fires: two residents of Solano County, three in Napa County, a pilot who was on a water-dropping mission in Fresno County, and a 70-year-old man in the remote community Last Chance, according to the Associated Press.

The blazes started early last week, primarily because of the lightning storm, though Gov. Gavin Newsom said gusty winds and a heatwave exacerbated the fires. A statewide emergency has been in effect since August 18.

Where California's fires are burning

The biggest of California's fires is the LNU Lightning Complex Fire, which has burned about 368,870 acres in Napa, Sonoma, Lake, Yolo, and Solano counties, according to Cal Fire. Five people have died, and two emergency workers and two civilians have been injured. At least 1,080 buildings have been destroyed and more than 270 damaged.

The complex fire — the term for multiple fires in one region — is the second-largest in California's recorded history, though it's only 200 acres bigger than the state's other giant blaze, the SCU Lightning Complex Fire. It's 33% contained.

The SCU Lightning Complex Fire, meanwhile, is located southeast of San Francisco. The blaze, which began August 18, has expanded to encompass nearly 368,670 acres across six counties: Alameda, Contra Costa, Santa Clara, San Joaquin, Merced, and Stanislaus. It has injured at least five people and prompted evacuation orders in five of the six affected counties. (Contra Costa is the only one currently without such orders.) The fire is 35% contained.

In San Mateo and Santa Cruz counties, yet another wildfire, the CZU August Lightning Complex Fire, prompted evacuation orders for 64,600 people, killed at least one person, injured three, and destroyed more than 160 structures. The fire began in the Santa Cruz Mountains and has expanded to more than 81,000 acres. It's at 21% containment.

Two additional fires in Monterey county, the Carmel and River Fires, have grown to over 55,000 acres collectively, though both are over 50% contained. More than 100 structures have been destroyed and at least four people injured. The blazes also prompted thousands of evacuations.

And farther north, the Butte/Tehama/Glenn Lightning Complex Fire has burned more than 55,000 acres, destroyed two structures, and injured one person. It's 30% contained.

COVID-19 outbreaks in prisons led to firefighter shortages

California has relied on incarcerated people to fight wildfires for decades; the state has 3,500 inmate firefighters, making up approximately 25% of the state's total of 15,500 firefighters.

But the state has fewer incarcerated firefighting crews this year than usual, largely due to COVID-19 outbreaks in some prisons and an early release program by Newsom to protect at-risk people in prisons from COVID-19 outbreaks.

"What we have typically is 192 CDCR [California Department of Corrections and Rehabilitation] fire crews statewide," Cal Fire spokesman Brice Bennett told Insider on Monday. "When COVID-19 came around, we went down to 90."

By Monday, the state's number of inmate crews had gone back up to 112, Bennett said.

Still, the size and strength of the fires are stretching California's firefighting resources, according to the LA Times. Governors in Nevada and Arizona have agreed to send crews to help, and Newsom authorized the hiring of 800 additional seasonal firefighters, Bennett said.

Poor air quality throughout the region

Much of California has felt the fires' impacts in the air over the last week, though many regions saw some relief on Wednesday and Thursday.

Most of the state's northern and central counties have reported unhealthy air quality on and off, with some reporting hazardous outdoor air. Bay Area residents have seen falling ash, according to SFGate. The area's Air Quality Management District issued "Spare the Air" alerts through Friday, which prohibit residents from burning wood.

Ashy skies were reported last week as far away as Shasta Lake, more than 200 miles north of Napa and Sonoma counties.

Usually when air quality suffers, fire-safety experts recommend staying inside as much as possible and wearing N95 masks when outdoors, since those filter out smoke particles. But given the a nationwide shortage of N95s, many Californians lack effective masks.

Climate change is increasing the frequency and severity of wildfires

The wildfires erupted toward the end of a heat wave across the western US, which caused temperatures to top 100 degrees Fahrenheit in parts of Northern California.

Climate change increases the likelihood of extreme heat events: The 10 warmest years on record overall have all occurred since 1998, according to NOAA. After a heat wave in Europe killed 70,000 people in 2003, researchers calculated that climate change made such a heat wave four times more likely.

Of the 10 most destructive wildfires in California's history, nine have occurred since 2000.

The hotter and drier land gets, the likelier fires are to occur. A recent analysis by Stanford University found that average temperatures during wildfire season in California have risen by more than 2 degrees Fahrenheit, while precipitation has dropped by 30%. Those conditions have more than doubled the state's total number of extreme wildfire risk days in autumn.

But the trend isn't limited to one state. Large wildfires in the US overall now burn more than twice the area they did in 1970. In the western part of the country, the average wildfire season is 78 days longer than it was 50 years ago.

Rhea Mahbubani and Frank Carber contributed reporting.