The biggest challenge you are going to have that time of year is short approaching the winter solstice. But SEA is the same. Ice is a freak event, as others have suggested.

If I was you, I would consider renting a bike. Lots to see & do, incl. doing the iconic cycling path around Stanley Park! UBC is very nice (NB much nicer campus than U of Washington). Public transit is also outstanding esp. since the Canada Line was added. There is also a night market in Surrey/Richmond worth checking out!