A wildfire burns behind a home in Twisp, Washington, in August. Authorities urged people in the town to evacuate because of the fast-moving blaze. (Ted S. Warren/AP)

The nation is closing in on its worst wildfire season in recorded history, with nearly 9.8 million acres already burned — the equivalent of Massachusetts, Connecticut, Rhode Island and part of New Hampshire going up in flames.

Two large fires and more than 160 smaller ones remain active, and more fires are expected to be reported before the month ends. Together, they’re likely to push the 2015 total past the record 9.87 million acres burned in 2006.

The extent of scorched earth reflects a warming trend that has made the United States considerably drier, scientists and fire expects say, with less mountain snowpack particularly in Alaska and the southwest.

“Over the winter we had real low snow fall,” said Tim Mowry, spokesman for the Alaska Division of Forestry. “Then we had a record lightning bust come in the third week in June — 60,000 strikes in a week. That resulted in 300 new fire starts because conditions were so dry.”

As Alaska deals with extensive wildfires, Levi Orr lays hoses out to dry in Fairbanks in mid-July. (Marc Lester/For the Washington Post)

Sheer numbers aren’t the only thing increasing. According to Wyoming state forester Bill Crapser, a vice president at the Association of State Foresters, fire seasons are starting earlier and lasting longer and the fires themselves get big faster. “We have more issues with them,” he said.

Agriculture Secretary Tom Vilsack said in September that $200 million a week was spent to battle wildfires nationwide. All told, some 30,000 people in at least a dozen states have been deployed for that effort — the largest force since 2000.

And to date, 13 firefighters have lost their lives across the country. More than 4,600 structures have been destroyed.

This summer, the growing severity of fire seasons prompted the Obama administration to ask Congress to adjust the formula by which it appropriates funds to fight bigger wilderness fires that are threatening homes and businesses.

Congress bases its funding on the average cost to suppress wildfires over a 10-year period. But three of the worst seasons ever have occurred in the past five years, and the Forest Service exhausted its $1.7 billion allotment to pay for firefighters and equipment well before the end of fiscal 2015. It was forced to borrow hundreds of millions of dollars from other departments within the agency.

The two big fires still being fought are not in the southwest, but in Kentucky, including in Daniel Boone National Forest near the Great Smoky Mountains.

Only four fire seasons have tallied more than 9 million acres burned. Alaska accounts for more than half of this year’s total, with 770 wildfires that so far have torched 5.1 million acres. That’s almost five times the average of typical years there.

Brandon Salzman of the Feather River Hotshots crew has a snack before heading back into Alaska’s Aggie Creek Fire. (Marc Lester/For the Washington Post)

The state used 2,800 people to fight and manage those blazes, and 55 structures near Anchorage were destroyed. But given that much of the affected acreage was remote wilderness, “it’s just not cost effective to put some fires out,” Mowry said. “There’s no people living there. No cabins, so to speak of, to protect.”

Bill Gabbert, editor in chief of Wildfire Today and Fire Aviation, has watched the season with some amazement. Much of the nation largely avoided catastrophe. States such as Arizona, New Mexico, Texas and Colorado escaped their usually catastrophic fires. Even Southern California, primed for disaster because it is bone-dry, was mostly spared.

On the other hand, Northern California, Washington, Oregon and Idaho were hard hit.

Amid Washington’s record drought, exacerbated by a near-zero winter snowpack, a rainforest in Olympic National Park caught fire and slowly burned through July. In Oregon, the season was deemed historic in September for the most number of fires “that have threatened or are threatening communities, closing highways and freeways, impacting entire towns,” said Joe Hessel, a forester in the state’s northeast district.

The country was fortunate that the number of burned acres in the lower 48 states fell well below their annual average of about 6 million acres, Gabbert said. Unlike in Alaska, in those states “you can’t just let a fire burn,” he said.

“I don’t have the expertise to blame this on global warming,” he noted, “but one thing the scientists say it will bring extremes in weather, and we had fires in extremes.”