A grand opening celebration for the State Route 99 tunnel through downtown Seattle is slated for February 2-3, 2019, the Washington State Department of Transportation announced Thursday.

WSDOT hopes to open the tunnel the following week, depending on the weather, according to David Sowers, deputy program administrator of engineering and operations at WSDOT.

Before the celebration, the viaduct will close January 11 for approximately three-weeks so crews can connect the on- and off-ramps to the tunnel and remove detours. The paving, concrete, and asphalt work is weather-dependent, but Sowers said WSDOT has built in some contingency into the three-week closure for poor weather concerns.

RELATED: Getting around after the tunnel opens: Driving southbound

RELATED: Getting around after the tunnel opens: Driving northbound

The weekend-long celebration will include a fun run and bike ride through the tunnel and on the viaduct, a ribbon cutting ceremony, and a festival. WSDOT says the events aim to celebrate the waterfront’s past, present, and future, and will include an art festival with 100 local artists on the viaduct, programming highlighting STEM and people who worked on the tunnel, and highlights of future plans for the waterfront.

WATCH: WSDOT announces Seattle tunnel celebration

The two-mile-long tunnel and the viaduct will be open Saturday between the Battery Street Tunnel and Seneca Street so people can walk the roadways for the first or last time. There will be a shuttle pick-up location at the south end of the portal.

The Saturday 8K fun run route will start at the north portal, run to the south end of the tunnel, and back north on the viaduct to the north portal. A 12.5-mile bike ride that turns around at South Idaho Street on SR 99 will follow a similar route Sunday.

WATCH: Animation of walk, run, bike routes

Two festival locations with live music and food trucks are planned for the north and south portals of the SR 99 tunnel, which are located east of Seattle Center and at South Royal Brougham Way. Roads will also be closed to traffic in the area near the festivals.

The public can register for event tickets on the Step Forward website. Tickets to walk through the tunnel and Viaduct on Saturday are free, but the fun run and bike ride require paid tickets.

The events are slated to occur rain or shine, although a snow and ice plan is being formulated.

Here’s a complete schedule of events:

Saturday

7:30 a.m. – noon – Fun run

11:30 a.m. – 12:30 p.m. – Ribbon cutting ceremony

11 a.m. – 6:30 p.m. – Public festival

12:30 p.m. – 6:30 p.m. – Public tunnel walk/access

12:30 p.m. – 6:30 p.m. – Goodbye to the viaduct/hello waterfront

Sunday

Sunrise – 11 a.m. – Bike ride

WSDOT took possession of the tunnel under Seattle from contractor Seattle Tunnel Partners on October 5. Work still needs to be completed, but the tunnel can operate as designed, according to WSDOT. That means if traffic had to go through the tunnel now, it could, although the roads leading to the tunnel aren't completed.

After the evening commute on January 11, travelers will experience the longest major highway closure in Puget Sound history. WSDOT will close the Alaskan Way Viaduct for three weeks from the Battery Street Tunnel to South Spokane Street so crews to realign ramps from SR 99 into the new tunnel.

The closure is necessary because crews will build the ramps and road connections on the current roadway.

WATCH: Animation of getting around the SR 99 closure

More coverage:

- SR 99 traffic projected to spike when tunnel opens in Seattle

- SR 99 tunnel toll rates will range from $1 to $2.25 in Seattle

- Seattle tunnel hits 'very important milestone' as state takes control

- 3-week Viaduct closure coming ahead of Seattle tunnel opening

- Seattle tunnel tested for full-scale emergency

- Seattle tunnel delays: Why the project is 3 years late

- How tunnel delay could impact Seattle's waterfront

Join KING 5's Seattle Tunnel Traffic Facebook group to stay up-to-date on the latest Seattle tunnel and Viaduct news and get tips to battle traffic during the three-week Viaduct closure in January.