The choppers deployed a day after Gov. Chris Gregoire signed an emergency declaration for all the state's counties east of the Cascade Mountains.
On Friday, the governor ordered an immediate ban on all outdoor and agricultural burning in Eastern Washington.
With more warm, dry weather expected "the potential for additional fire activity remains incredibly high," she said, noting fire crews are "already pushed to the limits."
The ban that includes campfires, bonfires, yard clean-up and land clearing will last through Tuesday.
Seven large complexes of fires have burned across more than 230 square miles of parched land east of the Cascades, where some areas have gone without any measurable rain for weeks. More than 3,000 firefighters across the region dug lines and burned dry grass and brush in the path of the fires.
One of the largest fires - the Wenatchee River Complex - was 10 percent contained, but crews there said they had success on Thursday. On Friday, crews with air support worked to cool down hot spots.
The two helicopters are a CH-47 Chinook helicopter with a 2,000-gallon water bucket and five-person crew, and a UH-60 Blackhawk helicopter with a 660-gallon water bucket and four crew members, the National Guard said.
The pilots and crew are members of the Washington Army National Guard's 66th Theater Aviation Command, which also aided last month in the Taylor Bridge fire by dumping 632,000 gallons of water.
Heavy smoke continued to cover much of the region on Friday, eroding air quality but serving a positive sign of low winds and fires that weren't quite so active.
Cooling temperatures were forecast to move into the region over the weekend. But there is no sign of rain in the forecast. Firefighters hoped to take advantage of the favorable conditions before the weather shifts again.
On Friday, authorities lowered the evacuation warnings to the lowest level for nearly 160 homes in the Wenatchee area, said spokesman John Kruse.
About 10 miles from the Grand Coulee Dam, two fires grew to a combined 91,883 acres, or 143 square miles. That complex was 79 percent contained late Friday.
Fire officials in charge of another fire that has blackened more than 23,000 acres, or 36 square miles, about 17 miles southwest of Creston promised full containment by day's end Friday and said they planned no more updates. That fire burned about 50 miles west of Spokane.