How Weatherproof Are Yakima Roof Cargo Sky Boxes  

I have run my Yakima Skybox 21 extensively in the field and I have never had any water get inside it while it was closed up. I have read about others getting water inside. I can see how water might get inside if the Skybox is not fully closed, which is definitely possible and I have experienced that several times especially when I first started running it. There are two things that can happen where the Skybox appears to be fully closed, but it's not fully closed. The first is the more concerning of the two, the Skybox is able to close and the key able to be removed from the latching mechanism, but in actuality the Skybox is not fully closed. The way to know that the Skybox is fully closed is that the latch mechanism is completely in the "lock" or flush position (perpendicular to the ground) -AND- the key is able to be removed. If the key is removed but the latch mechanism is not completely in the "lock" (perpendicular) position, this indicates that one or more of the lock points (there are three on each side) may not be fully engaged. One user noted in their review that they had their Skybox fly open while on the highway because of this issue. Thus, make sure that the latch is completely in the "lock" position (perpendicular to the ground, not angled in any way). Test that the Skybox is fully latched by pushing up firmly against the lid on both sides every time before driving -- if pushing up firmly against the lid is able to rock the whole car, this indicates that the box is locked and also tests that the rack attachment points are locked. The other issue that could allow water to enter is when the Skybox is fully closed and locked but there is a gap usually toward the front of the Skybox but could also affect toward the rear of the Skybox. The gap is usually from overloading the front or rear of the Skybox such that the support platform droops slightly. It looks fully closed and locked, and it is fully closed and locked, but there's a small gap there and a strong downpour or extended storm could then allow water to pour inside. The water would pool along the bottom of the platform and could potentially wet everything sitting inside. To avoid this, check all around the sides of the Skybox to make sure that the shell flange is fully overlapping the platform flange. If any of the platform flange is visible, take some items out of that section or shift some items around to reduce the weight there or to reduce the height of the items in there since taller items can be pressed on by the upper shell and result in the same platform droop. That said, I have run the Skybox 21 plenty of times with the gap and still not experienced any water intrusion -- I have the gap issue less now that I widened the distance between cross bars to the maximum that would fit the Skybox. Yakima points to that the attachment points to the roof rack is not fully sealed. That is true, there is a running track for the roof rack attachment points which allows for adjustability. There is high-quality weatherproofing there to nearly completely seal the box from the outside, but it would be impossible to completely seal that and its possible water could get in that way from high speed winds and water deflecting upward from a windshield to the under-side of the platform. I have not experienced that on my set-up on an SUV roof but could affect other set-ups more.