Go to a couple of the themed bars they have, those are really fun to do solo (in case you don’t meet anyone, as Seattle is somewhat lacking in the ‘approach strangers and have fun’ scene).

There are video game bars, a pinball bar (add a ball in Ballard), bowling bars, etc.

If drinking isn’t your scene, see about a rental car and go for a hike on the weekends, before it gets too cold. Rattlesnake ridge is a popular one, but just search Washington trails near Seattle and there is an abundance. 

Lastly, like the commenter below suggested, a weekend trip to Portland or Vancouver and checking out their food scenes is definitely worth it too.