Whatcom County area fire growing in size on steep terrain near historic mountain lookout

A wildfire sparked by lightning in the North Cascades National Park grew in size Sunday near a historic fire lookout on Sourdough Mountain.

Park officials closed the Sourdough Mountain Trail and U.S. Forest Service firefighters were attacking the flames on the ground, assisted by a helicopter, according to park officials and an online report at WildCAD.

Flames and smoke were visible near the summit of the 6,113-foot peak in Whatcom County, according to posts and photos on social media.

“Warm and sunny afternoon weather, increased winds, and low humidity increased fire behavior on the lightning-caused Sourdough Fire,” the National Park Service said online.

Skies in the area were sunny on Sunday with temperatures in the low 80s, according to the National Weather Service.

Park officials said Saturday the fire was 5 acres and burning on Sourdough Mountain, above the Diablo Dam on the Skagit River.

A Sunday report on the Watch Duty app that tracks wildfire activity said the fire had grown to 15 acres with no containment.

Forest Service officials weren’t immediately available for comment and it was unknown if the historic fire lookout was threatened.

Sourdough Mountain towers above Diablo and the North Cascades Environmental Learning Center on Diablo Lake.

Its fire lookout, a frequent hiking destination, was built in 1933 by the Civilian Conservation Corps and is listed on the National Register of Historic Places.