The OWL is very waterproof. It is fully submersible to 200 ft of water for 24 hours.
That means it has an IPX8 rating.
To ensure your OWL is totally sealed from all of the elements, all you need to do is the following:
Keep an eye on the O-rings on each side of the body. Keep a very small dusting of lubrication on them. Us a non-petroleum-based synthetic lubricant. Tip: We like Slip2000
Ensure the O-ring under the bezel ring is centered and that the bezel ring is tight (no more than hand tight though). If you do that, your Cloud Defensive Light should be totally waterproof.