Back in the day many people had an issue when parking the car, since the AEM filter tilted up a little when installed and there was a water drain hole that drained water right on the filter (parking on incline made the issue worse). So a pool of water would collect in the bend of the intake tube. When the car would start up the water would be sucked into the engine.

I recall someone said they removed the filter and found a pool of water in the back of the pipe.

That is way people say plug the drain hole, or get a shield that covers the filter from the top. Driving in the rain/monsoon/hurricane won't do anything. driving into a small lake will hurt for sure.

But when I had an AEM V1, I had no issues, parking in the rain for hours etc...but than again my encounters with heavy rain are limited

 

That was with the original AEM CAI, if I'm not mistaken. I believe the bend was adjusted in the V2 and it no longer pools water.

 

V2 is great. Highly doubtful you are going to be submerging the car into enough water to mess it up. The latest design also has a duckbill (one way hole) at the lowest pipe area so the water would drain if it has to.

 

The V2 now has a duckbill drain valve at the bottom of the elbow. Mine has never held water. I didn't plug or cover anything.