Seattle Braces for Uncommon August Atmospheric River Bringing Heavy Rain

Seattle is preparing for an unusual atmospheric river event expected to arrive on Friday night, August 22, 2025, bringing significant rainfall during a typically dry month. This weather system is anticipated to deliver up to an inch of rain in the city and as much as five inches in mountainous regions. Meteorologist Logan Howard noted that the level of atmospheric moisture in the system is reaching daily record highs, making this event highly unusual for August. The rain is forecasted to fall over a 36- to 40-hour period and should taper off by Saturday morning.

This rare August weather event is expected to deliver up to an inch of rain in Seattle and as much as five inches in mountainous regions. While the precipitation may aid in combating the Bear Gulch Fire near Lake Cushman, which has burned over 8,000 acres since July 6, it also raises concerns about potential debris flows in areas like Mount Rainier National Park.

Background:

Atmospheric rivers are narrow corridors of concentrated moisture in the atmosphere that can deliver significant rainfall over short periods. They are common in the Pacific Northwest during fall and winter but are rare in August. The last significant August rainfall in Seattle occurred in 2015.

The Bear Gulch Fire is burning near Lake Cushman in the Olympic National Forest. As of August 14, 2025, the fire had grown to approximately 8,257 acres and was 3% contained. The fire has led to Level 3 "Go Now" evacuation orders for areas north of Lake Cushman, including the Dry Creek Trail, Staircase Campground, and regions across the causeway on the north side of Lake Cushman. Firefighters have faced challenges due to the steep and rugged terrain, making direct suppression efforts difficult.

Supporting Details:

Meteorologist Logan Howard noted that the level of atmospheric moisture in the system is reaching daily record highs, making this event highly unusual for August. The rain is forecasted to fall over a 36- to 40-hour period and should taper off by Saturday morning.

The anticipated rainfall could aid in suppressing the Bear Gulch Fire by increasing moisture levels and reducing fire activity. However, the effectiveness will depend on the intensity and duration of the rainfall.

Heavy rainfall on burned areas increases the risk of debris flows, particularly in mountainous regions like Mount Rainier National Park. Park officials have advised visitors to exercise caution near rivers due to the potential for fast-moving debris flows carrying mud, rocks, and other materials.

Quotes:

"The level of atmospheric moisture in the system has been reaching daily record highs," says Howard. "It's safe to say this is highly unusual for August."

Implications:

Residents and visitors in affected areas should stay informed about weather updates and heed evacuation orders and safety advisories.

While the rainfall may assist in fire suppression, it could also lead to soil erosion and water quality issues due to debris flows.

The upcoming atmospheric river presents a double-edged sword for the Pacific Northwest: offering potential relief in wildfire suppression efforts while simultaneously posing new challenges in the form of debris flows and other hazards. Vigilance and preparedness are essential as the region navigates this rare weather event.