I've used mine without a cover or case for almost 3 years now and I've been out in some of the worst weather you could imagine along the coast (horizontal rain in force 9-10 gales, getting a sandblasted face isn't pleasant

), and the only problem I've had is condensation under the screen cover, but that soon clears out on it's own. I think as long as you don't drop it directly into a puddle, the sea, or any water while it's switched on it's a pretty hardy unit. Had a look inside the other day and there's no corrosion at all.

While others run for the trees or shelter I'm usually the only one out detecting during the rain on club digs. For some reason the AT-Pro users are the first to run for the trees, even though those machines are meant to be waterproof.
A cover is probably sensible just to protect it from scratches but don't forget to remove it after every outing or the moisture trapped inside will probably start to cause problems. Unless you've put silica gel inside already.
Now I've said all this 'sods law' states mine will go wrong tomorrow.
