As you can see, this is a common occurrence. You either let it sit, or bring the slides in to allow it to run off. A small breeze or wind, will often move it enough to push the water off. The one thing to be aware of if it freezes after. In this case it will make a loud crashing noise when the slide is coming in. To prevent this, bring in the slide to dump the water before going to bed. If this all occurs in the middle of the night, then freezes, and you're leaving in the morning, the best thing is to get up there with a ladder and push the ice off before bringing in the slide. The ice thing probably occurs every couple of years for us, so the benefits of having slide toppers far outweighs the infrequent problems.