Right now there is a good fare on Air Canada that is pricing at only $289.83 roundtrip from Newark. Search dates on Orbitz like I did here. Check availability from September, 2017 through early April, 2018.
Deal Alert $290 Fare NYC To Vancouver
Sample Dates: 9/17-9/23 and 9/15-9/20
Make sure to use a card that will earn you bonus points on your airline purchase, like the The Platinum Card® from American Express which earns you 5X points for flights booked directly with airlines or the Premier Rewards Gold Card from American Express which earns you 3X points for flights.
Post more dates as you find them.