My one attempt at shooting in the rain was a little dicy. I got a rain cover that goes over the camera and tight around the hood of the lens. Changing lenses is possible, if you have an umbrella. But be careful about condensation, as if you're using a rain cover the warmth of your hands may cause the rain cover to fog, and so you can't see the images on the back screen well; if your lens or sensor is fogging over, you wouldn't really know. Anyway, I recommend you to take an brolly, at least to cover your gear whilst you're sorting out your lenses and things. Oh, and my gear spent the best part of the next day in the sun drying out, lenses and all.