Portable Air Conditioner? Window/Water Issues
They don't work as well as regular window units and they cost 3X as much. Newer AC's are lighter and can be pulled out quickly if need be. Properly installed, you should get no water. I've had different ones in different windows for 40 years and never had a leak or drip. It must be level. You may want to consider an awning over the window. Keeps the rain off of it and keeps the AC cooler.
Answer:
Some should be slightly tipped down towards the outside to ensure that the condensate drips out the back instead of overflowing out the front. 1/4" should do it. It's generally better to have a custom hole cut for the AC than trying to adapt it to a window opening, because a pre-existing window opening is usually vastly too big, you're trying to balance the thing on window jambs, and their flashing arrangements seldom work well. Ours are openings cut thru stick/vinyl siding, fully flashed and properly vapor barriered, just like a window, with supporting brackets to ensure that they don't move, and insulation stuffed in the gaps. One of them is screwed in place using angle iron. It ain't going nowhere, and neither of them have ever leaked moisture. But they are under eaves with too many trees around for direct wind impact. Second the through wall mounting recommendation. When mounting through wall you can use proper flashing techniques to prevent water getting in that are not possible with a window mount. You also don't loose the light from and use of the window.