Rule of thumb is put them on after Halloween! When it starts dipping down into the single digits it's probably a good idea.
Multiple sources reporting snow for the weekend.
http://www.weatheroffice.gc.ca/city/pages/bc-74_metric_e.html
http://www.theweathernetwork.com/weather/cabc0248/
http://ca.weather.yahoo.com/canada/british-columbia/vancouver-9807/