One of my favorite (and longest, that I've been on) hiking trails in Juneau, Alaska is Herbert Glacier Trail. It's perfect for a rainy day, which there are a lot of, because all of the thick trees cover you the majority of the hike, so you don't end up sopping wet. At least when it's only drizzling or a light rain.

If you want to make it all the way to the end, and I recommend it, that's where the view of Herbert Glacier is...prepare for a very long walk. About halfway through there's a pretty lake with gorgeous mountain views and a nice bench to rest. It's pretty much all flat walking trails though, so it's not too terrible. Just make sure to bring food and water. And of course, watch for bears!