Every now and then there's a total eclipse of the sun, but rarely is it as high-profile as the one expected over the continental U.S. in August.

NASA says a solar eclipse will track across North America on the afternoon of Aug. 21, with a total eclipse anticipated over 14 U.S. states. A total solar eclipse occurs when the moon perfectly aligns with the sun in the sky, effectively blocking its light and casting a shadow on part of the Earth below.

The remaining U.S. states and most of Canada will witness the phenomenon as a partial eclipse, with the moon obscuring part of the sun.

Canadian astrophysicist Jesse Rogerson, of the Canada Aviation and Space Museum, says it'll be an "unprecedented" opportunity for North American skywatchers to catch a glimpse of this rare occurrence, which hasn't occurred over the U.S. since 1918.

The total eclipse will be visible in Oregon, Idaho, Wyoming, Nebraska, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina and South Carolina, NASA says.

"It's a once-in-a-lifetime opportunity for those that live in those states," Rogerson told CTV News Channel. "It's really really accessible, not only for the people who live along that track, but also for us."

He says the eclipse is a perfect excuse to plan a trip to the United States, if you want to witness it first-hand.

"You want to be right in the middle of the width of that path," he said. He added that it's hard to know at this point what the weather will be like on Aug. 21, but generally speaking, west-coast states tend to have fewer clouds.

"You wouldn't want to go to a place that has a lot of cloud cover historically," he said.

Solar eclipses occur a few times each year, but oftentimes they appear over inaccessible parts of the globe, such as the middle of an ocean. Rogerson says this one is special because it's "the first time in 100 years that a solar eclipse track has gone all the way from the west coast of the United States to the east coast."

How to watch the eclipse

Whether you're watching the full eclipse from the central U.S., or taking in the partial eclipse from somewhere in Canada, Rogerson says it's important to use the proper equipment to protect your eyes.

"You need to be safe," he said. "You can't just look at the sun with your eyes, and you can't do it even if the moon is covering most of it."

Rogerson says solar eclipse viewing glasses are extremely cheap and easy to find at libraries and any branch of the Royal Astronomical Society of Canada. These paper-and-plastic glasses, which resemble 3D glasses, are specifically designed to protect the eyes while looking directly at the sun.

"You can't just use normal sunglasses. That is not a safe way to do it," Rogerson said. "There are safe and simple and cheap ways to do it, you just have to search it out."

For those who will be stuck indoors at the time of the eclipse, NASA will be live streaming it from several locations, meaning you can watch at your leisure and – most importantly - you don't need to wear special glasses.

The next total solar eclipse over North America is expected for Apr. 8, 2024. That eclipse will pass over much of the U.S. as well as parts of Eastern Canada, including Toronto, New Brunswick, Nova Scotia, P.E.I. and Newfoundland.

The last total solar eclipse over North America happened in Nunavut in 2008.