The Apostle Islands lie in a Lake Superior setting known for cold temperatures, rough seas, fog, and sudden squalls, where rocky shorelines reflect the surrounding water, land, forests, and history. Boaters and paddlers should monitor marine weather forecasts and remain constantly alert to changing conditions. Average daytime high temperatures range from 60 degrees Fahrenheit in May to the upper 80s in midsummer to the mid-60s in September, while average lows vary from 40 degrees in May to the upper 50s in midsummer to 50 degrees in September. Average water temperatures in May and June are only in the 40s.