Closures of both I-405 and the 520 bridge Saturday and Sunday are predicted to cause major backups on both the freeways and surface roads.
I-90 and I-5 will both be construction-free, allowing drivers to take alternate routes and hopefully keep traffic flowing.
All northbound lanes through downtown Bellevue are shutting down from SE 8th to 520. Drivers already on the Eastside can use Bellevue Way northbound around the closure.
520 is closed in both directions from 405 to Montlake for an annual inspection, and to put in a fish culvert on the Eastside.
Those heading south out of Seattle are also bound to run into traffic congestion in Tacoma.
From 10 p.m. Friday, July 12 to 4 a.m. Monday, July 15, each direction of SR 16 will be reduced to two lanes and both directions of traffic will use the 2007 bridge to cross the Narrows, according to WSDOT. The heaviest traffic congestion is anticipated between 11 a.m. and 5 p.m. on Saturday and Sunday.
Additionally, the Mariners will be playing at home, which will likely compound the problem in the south end of the city.
The closures are necessary, WSDOT says, to ensure the safety of the two main arterials.
"There's a lot of work to be done," said Lorena Eng, WSDOT's Northwest regional administrator, in a press release, "but combining it in one weekend helps reduce the number of closures we need this summer."
Eng says that packing it all into this weekend is also due to the full roster of summer events.
"We also want to avoid conflicts with special events like Seafair, the Bite of Seattle and the Bellevue Arts Festival."
Motorists are encouraged to plan their driving routes around the closures, and to leave extra time to get to their destinations.
For live updates: WSDOT Twitter