Photo: The Canadian Press. All rights reserved.

John Johnson returns to clear out and salvage remnants of his burned down home on Chiliwist Road, after the Carlton Complex fire burned through the valley, near Malott, Wash., on Sunday, July 20, 2014. (AP Photo/The Seattle Times, Marcus Yam) 

Wetter, cooler weather has helped firefighters make progress in their efforts to get the largest wildfire in Washington state's history under control.

With more rain in the forecast, they just hope too much moisture doesn't lead to flash floods after so much ground vegetation has been burned away.

The Carlton Complex of fires, which has burned nearly 400 square miles in the north-central part of the state, was 16 per cent contained as of Tuesday, fire spokeswoman Jessica Payne said. A day earlier, the fire was just 2 per cent contained.

The National Weather Service issued a flood watch from Wednesday morning through Wednesday evening because of expected heavy rainfall.

"It takes as little as 10 minutes of heavy rain to cause flash flooding and debris flows in and below areas affected by wildfires," the advisory said. "Rain runs off almost instantly from burned soils ... causing creeks and drainages to flood at a much faster rate than normal."

Still, the weather change was a positive development.

"The cooler weather and the moisture has cooled aspects of the fire down," fire spokeswoman Susan Peterson said Tuesday evening. "In some instances, firefighters were able to do a direct attack.

"We had additional crews come in, and they were able to put lines in closer to the fire itself."

Speaking at a fundraiser Tuesday in Seattle, President Barack Obama said the wildfire, along with other Western blazes, can be attributed to climate change.

"A lot of it has to do with drought, a lot of it has to do with changing precipitation patterns, and a lot of that has to do with climate change," the president said.

Obama also said Federal Emergency Management Agency Director Craig Fugate had authorized an emergency declaration to ensure communities that lost power because of burned power lines and poles get electrical power.

At more than 250,000 acres, the Carlton Complex is larger than the 1902 Yacolt Burn, which consumed 238,920 acres in southwestern Washington and was the state's largest recorded forest fire, according to HistoryLink.org, an online resource of Washington state history.

The fire is being blamed for one death. Rob Koczewski, 67, died of an apparent heart attack 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.

The number of homes destroyed in the Carlton Complex fire remained at 150, Payne said. Two structures, an outbuilding and a seasonal cabin, were confirmed destroyed Tuesday in the Chiwaukum Creek Fire near Leavenworth, she said.

More than 2,100 firefighters and support crew are involved with fighting the fire, Payne said. She said firefighters have had success with fire lines on the east side of state Highway 153 between Carlton and Twisp.

Karina Shagren, spokeswoman for the state's Military Department, said the National Guard has already been offering aerial support, but 100 National Guard troops were now being used on the ground for firefighting, and additional troops were receiving firefighting training for potential future use.

Fires are currently burning in Oregon, Washington, Idaho, Utah, Arizona and California, and both Oregon and Washington have declared states of emergency.