WSDOT’s whirlwind interstate closure schedule may have some late night and early morning drivers on edge this weekend, so plan ahead before taking a trip on I-90 or I-5 from 11:30 p.m. Friday, July 31 through 10 a.m. Sunday, August 1.

Crews will close eastbound I-90 on Saturday, July 31, and westbound I-90 on Sunday, Aug. 1, between Rainier Avenue and East Mercer Way, to inspect more than a dozen sign bridges.

On Saturday, July 31 crews will close eastbound I-90 from 12:01 a.m to 10 a.m. between Rainier Avenue and East Mercer Way, as well as the Rainier Avenue and Island Crest Way on-ramps to eastbound I-90. All drivers will be diverted onto the express lanes.

The following day, Sunday, August 1 crews will close westbound I-90 from 12:01 a.m. to 10 a.m. between East Mercer Way and Rainier Avenue. All drivers will be diverted onto the express lanes. The Island Crest Way and 77th Ave. S.E. ramps to the express lanes will remain open; all other westbound ramps on Mercer Island will close.

The full closures are needed so crews can maneuver large pieces of equipment across the roadway and access all sections of the sign bridges. Crews will also perform other maintenance and safety tasks.

Crews will close all lanes of southbound I-5 from 11:30 p.m., Friday, July 30, to 4 a.m., Saturday, July 31, to test the fire suppression system under the convention center. The on-ramps from Howell/Yale Street and Mercer Street to southbound I-5 will also close.

Drivers will be detoured off I-5 at Stewart Street and re-enter I-5 south of the convention center.

The I-5 express lanes will open in the southbound direction at 11:30 p.m., Friday and remain southbound until noon Saturday.

Call 511 for traffic updates .