If water can get in, it will. Water ingress is the most common cause of external fittings failing. Try to design out points of failure by planning each link in the chain: the fittings themselves, the connections and the overall approach to cabling.
We’ve written a longer post on how to design out points of failure on the blog but in summary it’s important to take a end-to-end view of each circuit. Use high quality fittings, we’ve a selection on the website, and make all connections in the driest environments you can. We frequently supply LED fittings with extra long tails, 15m or longer, to allow electricians make the connections between fittings and drivers in internal locations.