Plan ahead for another busy weekend of highway construction across Puget Sound, Aug. 21-24

Expect congestion and delays on I-5, I-405, SR 520 and SR 99

SEATTLE - The Washington State Department of Transportation will have multiple highway construction closures during the Aug. 21-24 weekend, and travelers should plan for longer travel times across the Puget Sound region.

People will encounter delays on major north-south routes on Interstate 405, I-5 and State Route 99 as well as going eastbound from Seattle to Bellevue. Travelers should expect:

• Full closure of southbound I-405 from Bellevue to Renton.
• Full closure of the SR 520/Montlake Boulevard interchange.
• Closures on portions of SR 99.
• Continued two-lane configuration on northbound I-5 across the Ship Canal Bridge.

The work is spread across the region, but the effects overlap as travelers adjust routes and traffic shifts between highways and local streets. People should expect congestion, allow more time to travel and check conditions for their entire trip before leaving.

Southbound I-405 closure from Bellevue to Renton

Southbound I-405 will close from Coal Creek Parkway Southeast to North 30th Street from 11:30 p.m. Friday, Aug. 21, to 4 a.m. Monday, Aug. 24.

The following on-/off-ramps will be closed:

• Coal Creek Parkway Southeast on-ramp to southbound I-405
• Lake Washington Boulevard on-/off-ramps (Exit 9)
• Northeast 44th Street on-/off-ramps (Exit 7)
• Southbound I-405 off-ramp to Northeast 30th Street (Exit 6)

Crews will work on drainage, repaving and a traffic switch as part of the I-405/Renton to Bellevue Widening and Express Toll Lanes Project. A southbound detour will be in place.

SR 520/Montlake Boulevard interchange closure in Seattle

Montlake Boulevard will close between East Hamlin Street and East Louisa Street from 10 p.m. Friday, Aug. 21, to 6 a.m. Monday, Aug. 24.

The following ramps and surrounding streets will close:

• Montlake Boulevard on-ramps to eastbound and westbound SR 520.
• Eastbound SR 520 off-ramp to Montlake Boulevard.
• A 300-foot-long section of East Roanoke Street west of Montlake Boulevard.
• Lake Washington Boulevard between Montlake Boulevard and 24th Avenue East.

The westbound SR 520 off-ramp to northbound Montlake Boulevard will remain open. Crews will maintain a path for people walking, biking and rolling to cross SR 520 on Montlake Boulevard, with a limited detour south of SR 520.

Crews will install new sign structures on Montlake Boulevard. This work is based on community recommendations developed in 2024 (PDF 2.4MB) following concerns about the size and appearance of the current structures.

Northbound SR 99/First Avenue Bridge closure in Seattle, Aug. 22-23

Northbound SR 99 will close at the First Avenue South Bridge from 5 a.m. Saturday, Aug. 22, to 11:59 p.m. Sunday, Aug. 23 for bridge and structure preservation work. Travelers will not be able to access East Marginal Way or Michigan Street from the First Avenue South Bridge or continue northbound on SR 99 during the closure.

Additional closures include the:

• Occidental Avenue South/South Kenyon Street connection to northbound SR 99.
• West Marginal Way South/South Holden Street connection to northbound SR 99.
• First Avenue South connection to northbound SR 509.

Northbound I-5 lane closures across Ship Canal Bridge

Northbound I-5 in Seattle is reduced to two lanes across the Ship Canal Bridge until the end of 2026 as part of the Revive I-5 Ship Canal Bridge Preservation project. The express lanes will remain open northbound-only 24 hours a day. The Harvard Avenue on-ramp to northbound I-5 is closed until mid-October.

Plan ahead

Travelers should expect longer and less predictable trips. Delays may occur in new places and at new times, and conditions may change week to week as summer construction work moves around the region during the good weather window needed for much of this work.

To help ease congestion and delays, people can use transit and park-and-ride options, be flexible about travel times and access real-time traffic information. Drivers should slow down, stay alert and follow posted signs when approaching and traveling through work zones. These choices can make a meaningful difference during major closures and help keep both travelers and highway crews safe.

Much of this work requires good weather and may be rescheduled due to rain. Schedule updates will be available on WSDOT's online Travel Center map, the WSDOT mobile app and by signing up for WSDOT's King County email updates.