Do I need a rain\snow cover on this furnace vent?
I have the same setup, and this appears to be the industry standard for high efficiency gas furnaces.

What I have done is take a piece of plastic screen, and hose clamped it over the end due to a couple of 5 year old hooligans that run around my back yard and find such outlets very attractive for the experimental dropping of pebbles and other small items.



WARNING -- There is a danger here of the screen condensing and freezing, thus blocking the exhaust.  You should remove it in winter time.  If your local five-year-old hooligans cannot be kept away in the winter, then check it often for freezing in extreme cold conditions.