"If things go well, it could up and running by mid-June," Gov. Jay Inslee said.
The temporary span would be able to carry regular-sized cargos as well as cars. The speed limit would be lower than the 60 miles per hour allowed previously.
Once debris is removed from the river, further underwater structural examinations will determine if additional repairs are needed before installing the temporary span.
The bridge will consist of two, 24-foot wide structures to replace the collapsed section of the bridge. The structures will be pre-built and trucked to the site to allow for faster installation. The remaining southern section has been examined and will not need to be replaced, according to Inslee's office.
Planners hope to have the temporary structures in place within three weeks, if the remaining inspections of the bridge structure find no additional damage.
The federal government is expected to cover 100 percent of the costs of the temporary bridge and 90 percent the replacement, said state Transportation Secretary Lynn Peterson.
"The plan minimizes the closure time and keeps clear access to popular Skagit County retail business and destinations including the Anacortes ferry terminal," Inslee said. "I'm proud of all the work done by the Department of Transportation and all our local and federal partners that resulted in this innovative plan."
Crews will immediately start work on the permanent bridge when the temporary span is put in place. They will put temporary piers into the river to support a platform adjacent to the collapsed span where the new section will be built. Once complete, the temporary span will be removed and the new permanent span will be moved into place.
On Thursday, a semi-truck carrying an oversize load clipped a steel truss, starting the collapse of the span and sending cars and people into the cold river waters, authorities said. The three people in the cars survived with non-life threatening injuries.
But the collapse cut access to one the most important highways in Washington state for trade, commuters and travelers.
Investigators with the National Transportation Safety Board are still focused on the broken bridge.
Investigators have traveled to Alberta, Canada to inspect the trucking company's records, Debbie Hersman, the agency's leader, said.
They're looking into the work, rest histories and cell phone records of the truck driver and the pilot car driver, who they want to interview.
NTSB also wants to talk with witnesses who may have seen evidence the pilot car's height pole hit the bridge first.
Hersman said Sunday the bridge had withstood other over height collisions with vehicles in the past, with the most recent reported collision happening last October. She said evidence of other collisions can be seen in the spans still standing over the water.
Hersman also said a second truck with a similar cargo was traveling behind the truck involved in the collision. She said investigators are inspecting that cargo and truck to take measurements. The truck involved in the collision has also been moved off the highway on-ramp where it has been parked since Thursday.
The NTSB head also said that if the truck had been on the left lane of the southbound lanes, it likely would have cleared the bridge without a collision, but added that more precise measurements need to be taken. The bridge's height clearance varies across it.
"We know the company was required to establish that they could clear the entire route," Hersman said.
The truck's cargo from Canada was headed to Alaska. Its plan was to load its cargo onto a barge in Vancouver, Wash., about 275 miles south of the border crossing.
Meanwhile on Saturday, barges arrived at the river with equipment ready to remove the mangled steel, pavement and cars in the water.
Associated Press writers Manuel Valdes, MIke Baker and Donna Gordon Blankinship contributed to this report.