SPOKANE, Wash. (AP) — Calmer winds and cooler temperatures were allowing firefighters to go on the offensive Monday against a destructive wildfire that has charred hundreds of square miles of terrain in Washington State and is the largest in state history.

The Carlton Complex of fires in north-central Washington had burned about 379 square miles, fire spokesman Andrew Sanbri said Monday. That would make it the largest wildfire in the state since record-keeping started.

“There is optimism in the air, but we don’t want to give the impression that all is good,” Sanbri said. “Things are improving.”

The fire was just 2 percent contained Monday.

But the news was not all good. The Okanogan County Sheriff’s Office announced mandatory evacuations Monday afternoon of rural areas south of Highway 20 between the towns of Twisp and Okanogan. That included the small town of Carlton. It was not immediately clear how many homes were involved in the evacuations.

Highway 20 was also closed because of fire activity

At 243,000 acres, the Carlton Complex was larger than the Yacolt Burn, which consumed 238,920 acres in southwestern Washington in 1902 and is the largest recorded forest fire in state history, according to HistoryLink.org, an online resource of Washington state history. The Yacolt Burn killed 38 people.

Firefighters planned to aggressively protect houses near Libby Creek on Monday by keeping the flames from jumping the waterway, Sanbri said. Okanogan County Sheriff Frank Rogers has estimated that 150 homes have been destroyed already, but he suspected that number could rise. The fire is being blamed for one death.

Firefighters on Monday had also planned to burn fuel on the north side of the fire to help build a fire line, but that operation was canceled, fire spokesman Don Carpenter said.

Firefighters were hampered by the loss of electricity in the area, thanks to downed power lines and poles, which hurt communications. There was no estimate on when utilities would be restored.

The forecast for Monday and Tuesday called for lighter winds and lower temperatures, said Spokane-based National Weather Service meteorologist Greg Koch.

Then on Wednesday a vigorous front is expected to cover Washington, bringing rain to much of the state. But it will also bring lightning, Koch added.

“The benefits of the system are still up in the air,” he said. “We may get some rain where we need it, but we may also experience some lightning that could cause some new ignitions.”

The fire has created smoky conditions and reduced air quality in much of eastern Washington and northern Idaho.

One man has died of an apparent heart attack while fighting the fire near his home, Rogers said.

Rob Koczewski, 67, was stricken on Saturday while he and his wife were hauling water and digging fire lines near their home. Koczewski was a retired Washington State Patrol trooper and U.S. Marine, Rogers said.

There are more than 1,600 firefighters battling the flames, assisted by more than 100 fire engines, helicopters dropping buckets of water and planes spreading flame retardant, Sanbri said.

Many towns in the scenic Methow Valley remain without power and have limited landline and cellphone service. Fully restoring power to the area could take weeks, Okanogan County Public Utility District officials told KREM.

A total of 100 National Guard troops were on standby, and up to 1,000 more in Yakima could receive additional fire training, said Karina Shagren, spokeswoman for the state’s Military Department. Active-duty military could be called in as well, Inslee said.