The declaration makes federal emergency aid available to supplement state and local response efforts in the area affected by wildfires.
The president's action authorizes the Federal Emergency Management Agency to coordinate all disaster relief efforts, and to provide assistance for emergency measures to save lives and to protect property and public health and safety.
The emergency declaration covers areas of Chelan and Okanogan counties as well as the Confederated Tribes of the Colville Reservation.
FEMA is authorized to provide equipment and resources necessary to alleviate the impacts of the emergency. Emergency protective measures will be provided at 75 percent federal funding.
Obama said Tuesday the emergency declaration would 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, and they planned to burn lines around Pearrygin Lake.