Even in May there might still be snow on the ground, especially in the wooded areas. Temperatures were far below average this year, and there was no mid-winter thaw like we usually get. Just months and months of temps well below freezing. Much of Wilderness sits pretty near lake level, and could be soggy depending on how our spring melt goes here in Northern Michigan.
The sites along the water vary from spacious to tiny, with many of the ones on the beach itself being uneven loose sand, not dirt or grass. The inland campground is where the modern showers are, and the sites are grass / dirt, and more uniform in size.