The Sourdough Fire was a

wildfire A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...

Whatcom County, Washington Whatcom County (, ) is a County (United States), county located in the northwestern corner of the U.S. state of Washington (state), Washington, bordered by the Lower Mainland (the Metro Vancouver and Fraser Valley Regional Districts) of the ...

, in the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

region of the United States. It was reported on July 29, 2023, near Sourdough Mountain in

North Cascades National Park North Cascades National Park is a List of national parks of the United States, national park of the United States in Washington (state), Washington. At more than , it is the largest of the three National Park Service units that comprise the No ...

and was likely caused by an earlier lightning strike. The fire caused the closure of the

North Cascades Highway North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north'' is ...

(State Route 20) and evacuations of recreational facilities and three

Seattle City Light Seattle City Light is the public utility providing electricity to Seattle, Washington, in the United States, and parts of its metropolitan area, including all of Shoreline, nearly all of Lake Forest Park, and parts of unincorporated King County, ...

hydroelectric dam Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...

s in the area. , the Sourdough Fire had been estimated to have burned and was 25 percent contained.

History

The Sourdough Fire was first reported on July 29, 2023, three days after a thunderstorm in the area with lightning strikes that caused nearby fires. It is named for Sourdough Mountain in

. The fire grew to over by August 4 and prompted the immediate closure of the North Cascades Highway ( State Route 20) between Newhalem and Rainy Pass. It was initially reported on August 5 to be nearly but the estimate was revised down with the use of more accurate mapping. The North Cascades Highway reopened on August 9, but closed again two days later due to increased fire activity near the road. Evacuations were ordered at several campsites and recreational facilities in the park around Diablo Lake. By August 11, the fire burned approximately and was 5 percent contained with 411 firefighters, 6 helicopters, and several aircraft dispatched to the area. The Sourdough Mountain Lookout, a historic

fire lookout A fire lookout (sometimes also called a fire watcher) is a person assigned the duty to look for fire from atop a building known as a fire lookout tower. These towers are used in remote areas, normally on mountain tops with high elevation and ...

tower atop the mountain, was wrapped in fireproof material to protect it from damage. The fire generated a large

pyrocumulus cloud A flammagenitus cloud, also known as a flammagenitus, pyrocumulus cloud, or fire cloud, is a dense cumuliform cloud associated with fire or volcanic eruptions. A flammagenitus is similar dynamically in some ways to a firestorm, and the two ph ...

on August 4 that was visible from the

Puget Sound region The Puget Sound region is a coastal area of the Pacific Northwest in the U.S. state of Washington (state), Washington, including Puget Sound, the Puget Sound lowlands, and the surrounding region roughly west of the Cascade Range and east of the ...

. Fire officials expect the Sourdough Fire to continue southeast towards Diablo Lake and Gorge Lake and potentially west where "more continuous fuels exist". The fire, described as "long-duration", is not expected to be contained until October due to warm temperatures and low humidity. The community of Diablo is expected to remain under evacuation orders, along with the

Diablo Dam Diablo Dam is one of three dams along the upper Skagit River in Whatcom County, Washington and part of the Skagit River Hydroelectric Project that supplies Seattle with some of its power needs. The dam was built in Diablo Canyon, a gorge of solid ...

plans to continue operating the three hydroelectric dams in the area and suspended its tours of Diablo Lake. During evacuations of staff on August 2, the Diablo and Ross dams went offline while Gorge Dam continued with reduced output of about 50 percent; and several transmission lines were also shut down to prevent shorting. Power generation at the Diablo and Ross dams resumed on August 9. The fire was directed west towards Newhalem by firefighters using "burnout techniques"; the area near Newhalem includes burn scars from a 2015 wildfire that would slow progress. The strategy was paused after a

red flag warning A red flag warning is a forecast warning issued by the National Weather Service (NWS) in the United States to inform the public, firefighters, and land management agencies that conditions are ideal for wildfire combustion, and rapid spread. These ...

was issued by the

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

for the Diablo area with a high temperature of recorded on August 13. Smoke from the fire moved southwest into the Puget Sound region, including

Seattle Seattle ( ) is the most populous city in the U.S. state of Washington and in the Pacific Northwest region of North America. With a population of 780,995 in 2024, it is the 18th-most populous city in the United States. The city is the cou ...

, on August 13 and caused worsened

air quality Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...

readings. The smoke from the Sourdough Fire and other fires in Washington and British Columbia returned to the Puget Sound region the following week and caused the air quality index in Seattle to reach 190 on August 20, the worst among major cities globally. The North Cascades Highway reopened on August 23 for through travelers, with stops prohibited and recreation areas remaining closed due to the Sourdough and Blue Lake fires. It closed a day later and was reopened on August 30 for travel with pilot vehicles to direct traffic. The North Cascades Institute cancelled all of their programs for 2023 as a result of the fire, which forced their on-site employees to evacuate from dormitories. Management of the Sourdough Fire was transferred from the Northwest Incident Management Team 8 to the

National Park Service The National Park Service (NPS) is an List of federal agencies in the United States, agency of the Federal government of the United States, United States federal government, within the US Department of the Interior. The service manages all List ...

on August 29 following successful containment measures. The fire's spread slowed after rainfall in early September as containment reached 25 percent; several campsites and recreation areas in the North Cascades National Park Complex were reopened on September 11 due to improved conditions.

References

External links

InciWeb
{{Washington wildfires 2023 Washington (state) wildfires July 2023 in the United States August 2023 in the United States History of Whatcom County, Washington North Cascades National Park