Mine was classified as rain proof and I have been through some major storms for hours with no ill effects over 12 months and 10,000miles. Sometimes display goes a bit funny in very hot sun (100+), but again no long term problems.
Couple of points, to make it as accurate as possible take the wires straight from the display to the battery, don't go through a fuse or another 12v source.
It has no on off switch, but if you were leaving your bike for a few weeks, display would drain battery slowly.
The black dome below the display in the photo is an push on/off switch. I got it from a marine store and then put a small rubber dome over it-also from a marine store. Only a few $$'s, but I didn't want it on all the time.