Here’s every total solar eclipse happening in your lifetime. Is this year your best chance?

On Aug. 21, a total solar eclipse will be visible from the contiguous United States. It’ll be the first to traverse coast to coast in nearly a century. There will be 69 total solar eclipses visible from somewhere on the planet in the next 100 years, but only a few will be visible from North America. See how many total solar eclipses are left in your lifetime:

A total solar eclipse occurs when the moon aligns between the Earth and the sun. The shadow directly under the moon, called the umbra, is a total eclipse. The moon will also have a penumbra, which is a lighter shadow around the umbra. This is viewed as a partial eclipse. The path of the moon’s umbra as it moves across Earth is called the path of totality.

[Graphic: Travel the path of the solar eclipse]

On average, a total solar eclipse can be visible from somewhere on Earth every 1.5 years.

While all of North America will be able to see the eclipse on Aug. 21, most of the continent will only see a partial eclipse, which may or may not be noticeable depending on where you are. A total eclipse will only be visible along the path of totality, which is about 60 to 70 miles wide at any given point. The farther you are from this path, the less noticeable the eclipse will be.

The path of totality for the eclipse in August stretches from coast to coast — passing over Oregon in the west and moving all the way across the country to South Carolina in the east. This is a rare event; it’s the first time the path of totality will eclipse only over the contiguous United States.

[Everything you need to know about the Aug. 21 eclipse]

The last time a total solar eclipse occurred in the Lower 48 was 1979. The next time a total solar eclipse will traverse from coast to coast will be in 2045.

In the last 100 years, some areas have been in the paths of multiple eclipses: New England, for example, saw five. (During its World Series dry spell from 1918 to 2004, the greater Boston area alone saw two.)

Others weren’t so lucky. Just 200 miles away in New York, construction on the Empire State Building had not started yet the last time the city saw a total solar eclipse (1925). San Diego had a population of less than 100,000 the last time it was eclipsed (1923), and Chicago hasn’t seen a total eclipse at all in the last 100 years. An area near Tucson has the longest dry spell in the Lower 48: The last total solar eclipse it saw was in the year 797.

The U.S. mainland has averaged about seven total solar eclipses per century since 2000 B.C. Some areas have seen as many as 25 eclipses, while others, such as spots west of Minneapolis, have seen only four in the last four millennia.

Patterns in how eclipses traverse the country mean that some areas, such as the Midwest, get to see many more than others.

Even though you don’t have to wait long for the next total solar eclipse in the contiguous United States in 2024, it won’t be as expansive as the one coming up in August. But if you’re waiting for an eclipse to happen over your head, don’t hold your breath — you might be waiting for a couple of centuries.

Read more about the Aug. 21 eclipse:

Graphic: Travel the path of the solar eclipse

Everything you need to know about the Aug. 21 eclipse

Want to see this summer’s solar eclipse? Here are some viewing options across the U.S.

How to avoid clouds that could spoil the Great American Eclipse

Here’s what happened to people who tried to watch a solar eclipse without special glasses

The first solar eclipse to cross America in 99 years is coming. To some, it’s an act of God.

You’ll need special glasses to see the solar eclipse. Here’s where to get them free.