California’s Valley and Butte fires are still raging, but they’re already in the record books as some of the most destructive fires in the state’s history.

The Valley Fire, which exploded over the weekend in Lake, Sonoma and Napa counties, burning an area twice the size of Manhattan in 12 hours, now stands at 67,200 acres and 603 structures destroyed or damaged. That damage makes it the ninth-worst fire in state history. With the fire only 30 percent contained as of Wednesday morning, the ranking is likely to increase as investigators uncover more damage.

The Butte Fire, burning to the east of Sacramento, has also exacted a heavy toll on the state. The fire has charred nearly 72,000 acres and 408 buildings. That ranks it as the 14th-most destructive fire in state history, though again that number is expected to rise as the fire continues to burn.

“This likely will be, in terms of insured losses, the most damaging wildfire in northern California since the large Oakland wildfire in 1991,” Mark Bove, a senior meteorologist at Munich Re, said.

Bove said that combined damage from the Valley and Butte fires is comparable to the 2003 Old Fire, a wildfire in Southern California that damaged nearly 1,000 buildings and caused $975 million in insured losses. Adjusting for inflation and an increase in home prices, that likely puts these two fires in the $1 billion range for insured losses.

There are six large wildfires burning in California that have affected a combined 386,803 acres as of Wednesday. Together, they account for a quarter of all the large fires burning in the U.S. in what continues to be a record-setting wildfire season.

In total, 8.83 million acres have burned so far, an area nearly double the size of New Jersey. That puts this wildfire season ahead of all others for this time of year. It’s possible that when the last ember is snuffed out, this year could eclipse 2006 as the most destructive wildfire season in U.S. history in terms of acres burned.

The final cost of this year’s wildfire season is yet to be determined due the complex mix of agencies that collect damage data, but the widespread damage to buildings from the Valley and Butte fires likely mean insured losses will top $1 billion.

According to Steve Bowen, a meteorologist with reinsurance company Aon Benfield, insured fire losses have only topped $1 billion four times since 1990.

The link between those years? Destructive California wildfires.

“We expect that it’s likely that the Valley and Butte fires will be contained, but there’s potential for additional large fires to occur across the American West,” Bove said. “Where these fires occur will determine if there are additional large amounts of losses.”

Warm, dry conditions have dogged the western U.S. all year (and in California’s case, a lot longer) and turned the region into a tinderbox. Roughly 60 percent of the West is experiencing some form of drought, with the bullseye still over California.

Long-term, rising temperatures have contributed to an increase in the number of large wildfires and the acreage they burn. Wildfire season is also stretching 75 days longer as rising spring temperatures melt snowpack earlier and cool fall temperatures that can slow wildfire activity arrive later.