The moon will line up perfectly between the Earth and the sun, blotting out the sunlight. It will slice a diagonal line from the southwest to the northeast across North America, briefly plunging communities along the track into darkness or at least twilight.

REMEMBER: Don’t look at the sun without special glasses. This is true anytime, but the temptation is stronger during an eclipse, and the risks to damage your eyes are just as great.

Fifteen U.S. states will get a piece of the action, albeit two of them — Tennessee and Michigan — just barely.

Among the cities smack dab in the action: Dallas; Little Rock, Arkansas; Indianapolis, Cleveland; Buffalo, New York; and Montreal — making for the continent’s biggest eclipse crowd.

Don’t fret if you don’t have front-row seats. Practically everyone on the continent can catch at least a partial eclipse. The farther from the path of totality, the smaller the moon’s bite will be out of the sun. In Seattle and Portland, Oregon, about as far away as you can get in the continental U.S., one-third of the sun will be swallowed.

What happens on the ground near you?

• As the eclipse begins, the sunlight will grow dimmer, eventually becoming like twilight before dawn or just after sunset. If you are in a partial eclipse area, the light won’t become as dim as it will in areas of totalility.
• The temperature will fall. You may be able to tell it is cooler for a time.
• Street lights and other automated lights may turn on.
• If you are near wildlife or animals, they may behave differently, becoming quieter as they might normally at evening time.

Why is totality longer?

By a cosmic stroke of luck, the moon will make the month’s closest approach to Earth the day before the total solar eclipse. That puts the moon just 223,000 miles (360,000 kilometers) away on eclipse day.