A few of us have noticed that we have slugs in our overwintered hives. More than just one or two and all sizes. Can't see how some of them get in they are so big. Not sure whether they annoy the bees. I read one place that said bees don't like to touch them because they are so slimy.
Some people are against the use of products like Sluggo but Sluggo really works. I've put it around all of my hives. I don't think it has to be replaced after a rain.
For folks with new colonies you might want to do it sooner rather than later.