Cool and damp, cloudy and rainy for the most part, and that holds true from about late September to May. Not saying there are never any nice days during that time, but it's mostly damp. Average winter temps are in the 5C range. It does get below freezing from time to time, there can be snow but often there isn't much and it doesn't stick around long though it can stay for a few weeks. Coldest time of year is from about now to the end of January/early February. By late February, spring is definitely on its way with spring flowers coming out. It can be a long time arriving, but it's coming.
Summers are very nice, very often dry for long periods, but a bit cooler on average than most other parts of southern Canada. It can be much warmer even not all that far from the ocean which moderates all temperatures. The Fraser Valley communities such as Abbotsford and Chilliwack can be a few degrees warmer than Vancouver in summer, a bit cooler in winter.
Warmest city on the coast, I think, is Victoria. It gets less rain and more sun, though more wind, than Vancouver. Areas just outside Victoria have the longest growing season in Canada, I believe.
The interior of BC, like Kelowna in the Okanagan Valley, can have very hot summers but the winters are cooler. However, it's very dry there and it's true what they say about it being a "dry cold". When the air is dry, you feel the cold less. With dry air, some sun, and no wind, temperatures right around freezing can feel the same way quite a few degrees warmer does in humid eastern cities.
You can check weather stats at Environment Canada, and the Weather Network also has ways you can check past weather as well as current weather.