I forgot to mention, that Ive seen this kind of vent and although in a perfect world, the rain would go into the vent and into the furnace and drain out the drain on the furnace. Certainly no way ideal, as I've had to pour water out of the furnace that got full of water. ALL vent terminations should be protected from ingress of water, either by direction, turning down, whatever will work. I normally turn the intake down with a 45 or 90 depending on the case, and then raise the exhaust up a bit above the intake, a foot or so, and then turn it down the same.