For a few brief minutes on Monday, a total solar eclipse will blanket sky-gazers across the contiguous U.S. in a stunning astronomical spectacle that wont happen again for another 20 years.

An estimated 31.6 million people live in the path of this years totality and millions more are expected to travel there to catch a glimpse of the celestial event, prompting some governments to launch emergency orders in anticipation of crowds.

Its kind of mind-blowing because it happens very quickly, Dr. Cristina A. Thomas, an associate professor in astronomy and planetary science at Northern Arizona University, told HuffPost of the stunning scene as the moon engulfs the sun. The animals start to react. The temperature drops. Its a really interesting experience from that perspective.

Heres everything you need to know about the eclipse and how to prepare for it, whether youre in the path of totality or not.