Traveling at an average speed of 12 mph (but sometimes going up to 30 mph), the monarchs cover about 80 miles a day. They can fly at heights of up to 2 miles. They travel an average of 1800 miles from the United States and Canada to the oyamel forests in Michoacan where they spend the winter before embarking on their return journey.
How the monarch butterflies are able to find their way to the same wintering grounds every year remains a great mystery. One hypothesis holds that a small quantity of magnetite in the butterflies' bodies acts as a sort of compass leading them to the magnetic iron which is found in the area of Michoacan where they spend their winters.
Read more about the Monarch migration from Debbie Hadley, About.com's Guide to Insects: Monarch Migration, the Longest Repeat Migration in the Insect World