It's been 40 years since a total solar eclipse was visible in the United States.

On Monday, Aug. 21, the event that millions have anticipated will unfold when the moon passes directly in front of the sun.

The path of totality stretches from Lincoln Beach, Oregon, to Charleston, South Carolina. In this swath, the moon will completely cover the sun and the sun's atmosphere, known as the corona. During an eclipse, a halo appears around the sun.

Outside of the path of totality, observers will see a partial eclipse.

However, storms and cloudy conditions may spoil the view for some.

AccuWeather Meteorologist Dave Samuhel said the best weather conditions will stretch from the interior Northwest into Kansas and Nebraska.

Clear skies will offer ideal views of the eclipse.

However, farther west, clouds could fill skies in Oregon, especially west of the Cascades and near the Pacific Ocean, Samuhel said.

In the Southwest, the timing of the eclipse will help in terms of cloud cover, AccuWeather Senior Meteorologist John Feerick said.

"There will continue to be some monsoonal moisture in place over the Southwest, but because the eclipse occurs, there a little earlier in the day and most of the thunderstorms are likely to occur in the afternoon," he said.

Along the Mississippi River in Missouri and Kentucky, where the greatest eclipse occurs, clear skies are likely.

"A spotty thunderstorm could bring localized clouds, but most of the day should be clear," Samuhel said.

A higher risk for scattered showers and thunderstorms is possible from Missouri to the Southeast coast. Fortunately, no area looks to be particularly cloudy.

While some indications point toward a potential tropical system forming north of the Caribbean next weekend, conditions could change, Samuhel said. At this point, the system will likely be offshore and impact the Southeast after the eclipse is over.

"Cloud cover may be an issue for viewing across the mid-Atlantic states with a storm system potentially moving through on Aug. 21," Freerick said. The timing of the storm may make a big difference in the viewing conditions across the northeastern U.S.