Unable to survive the cold winters of North America, millions of these incredible butterflies travel 50-100 miles a day to reach the forests of central Mexico at the same time every single year. All told, they make an epic journey of more than 3,000 miles — the only species of butterfly to undergo such a long migration. How can their tiny, fragile wings get them so far? The USDA Forest Service writes, "Monarchs use a combination of air currents and thermals to travel long distances."But it is still a mystery how the butterflies are able to navigate with such accuracy, given the fact that it takes multiple generations to complete the journey. That's right — the butterflies that leave the U.S. and Canada in the fall won't make it back the following year.

Generally, the migration begins in October, as the temperatures start to drop and the butterflies leave in search of a warmer refuge.Their arrival in Mexico is truly spectacular, as millions of butterflies blanket the trees, the sky, and the forest floor (check it out in the video at the end of the post). If you ever want to experience such a phenomenon for yourself, you can visit one of four public sanctuaries within the Monarch Butterfly Biosphere Reserve, a World Heritage Site bordering Michoacán and the State of Mexico. Getting there requires a hike or a horseback ride deep into the forested mountains to reach the oyamel fir trees where the butterflies settle.Mexperience says: "The best time to see the butterflies is between late January and the end of March: before late January, the air temperature is cooler and the butterflies don't flutter as much."

You better get there in the next decade, though. Habitat loss, food scarcity, and herbicide use are causing monarch populations to plummet. Some populations have dropped up to 90 percent in the last 20 years. In 2018, unusually severe rainfall and cold weather in the States also impacted the butterflies' migration and delayed their arrival in Mexico by several weeks.

You can help keep the species alive by planting milkweed in your garden (or not cutting it down if it's around your house). Monarchs need it to survive, and herbicides are decimating the plants around the country.You can watch video below: