Climate
At a latitude of 48°North, and with the moderating influence of cold Lake Superior, Isle Royale rarely gets hot by human standards. During the summer months you'll reach shorts-and-t-shirt weather in the afternoon, especially hiking up on the ridges, but you'll also experience some rather chilly nights, sometimes even below 50°F 10°C in the "heat" of August. In May and October, temperatures can easily dip below freezing by night and stay below 60°F 15°C all day. Rainfall fluctuates from month to month, but July and August have the least overcast days making them the busiest weeks of the summer. Regardless, a stay of several days any time of the summer without at least some rain is uncommon; either bring rain gear or plan on spending time stuck in your tent or a shelter. The good news for people with hayfever is that they'll find few common pollen allergens in the air. During its resort days, the island was a popular haven for allergy sufferers. In the winter, conditions are inhospitable and the island is closed to all but wildlife researchers. Even the park headquarters relocate to Houghton for the winter.
History
Over four millennia ago, Native Americans began visiting Isle Royale to dig for copper, to tap maple trees for sugar, and to fish. Since Europeans came to the area, it's been host to whitefish fisheries, a series of unprofitable copper mining efforts, and a resort community around 1900. In the 1920s, Detroit News journalist Albert Stoll Jr. visited Isle Royale, saw what commercial exploitation was beginning to do to undermine the wilderness, and campaigned for its protection; a plaque in his honor was later placed near the tip of Scoville Point. Isle Royale National Park was established by Congress in 1931, and the last of the land de-privatized in 1940 with a few of the land owners given lifetime leases. The archipelago was designated a Wilderness Area in 1976, and named an International Biosphere Reserve in 1980.
Understand
Isle Royale is currently a wilderness preserve first, a sanctuary for those seeking to experience it second, and a travel destination third. Although it accommodates all of these uses, that's the order of priority they take. So wildlife gets the run of the island, and human visitors are generally restricted to established trails and accessible lakes, with leave-no-trace camping protocols in effect. Modern conveniences and comforts are very limited; away from the small ports on either end of the island, "running water" means "a creek", and only "outhouse" pit toilets are available. Many of the more accessible ones are stocked with toilet paper, but bring your own or be prepared to improvise.
Lake Superior winters close the park from November through mid-April, with limited access before Memorial Day and after Labor Day; Isle Royale is the only U.S. National Park Service park to shut down altogether for the winter. Because of this, along with its geographic isolation and challenging ruggedness, it receives fewer visitors in a year 17,500 in 2005 than many national parks endure in a day. Those visitors stay a remarkable average of 4-5 days each even counting day-trippers, but it still has one of the lowest visitors-per-square-mile figures outside of the huge Alaskan parks. Which is, of course, a large part of its appeal. And it leaves these visitors wanting more with the NPS's highest return-visit rate.
Landscape
The archipelago consisting of Isle Royale itself and dozens of smaller islands is the edge of a geologic fault which pushed up from the lake floor and was scoured by ice-age glaciers into a long, ridged island, with lakes and inlets of Lake Superior filling in low points between some of the ridges. The south sides of these ridges and the south lakeshore tend to be more gently sloped; the north sides and lakeshore more steep. Crossing from one side of the island to the other isn't usually a great distance, but because of the ridges can involve a lot of climbing and descending.
The island and its ridges run roughly WSW-to-ENE end to end, but for informal navigational purposes they're usually described as if they ran directly west-to-east a notion reinforced by the orientation of the park service's official map. When using a compass, keep in mind the island's true orientation. The Greenstone Ridge runs the length of the island, with a trail along most of its crest. Isle Royale itself is 45 miles 74 km long and 9 miles 14 km at its widest, with an area of about 205 mi² 530 km². The highest point on the island is Mount Desor at 1394 feet 425 m above sea level – about 800 feet 245 m above lake level – with several other spots along the Greenstone above 1200 feet 365 m in elevation.