Burlington, Vermont - Those along the path of the total solar eclipse on April 8 are preparing for the year's biggest astronomic event, with millions of visitors expected to brighten local economies – and snarl up logistics.

Near the US-Canada border in Burlington, Vermont, which is set to experience the totality just before 3:30 PM, many hotels have been sold out for months.

The few remaining rooms, which typically go for around $150 a night, show online prices of $600-$700 for the night of the eclipse.

"I don't know that we'll have anything quite like this again," Jeff Lawson, a vice president in the chamber of commerce, told AFP.

Lawson marveled at his city's "incredible luck" at an opportunity "quite literally falling out of the sky into your lap."

If skies are clear, the small city of 40,000 could see its population double for the day, with visitors arriving by car, train, and even private jet, Lawson said.

An estimated 32 million people live inside the "path of totality" – under which the Moon will fully block out the Sun – with an additional 150 million residing less than 200 miles from the strip, NASA says.

Preparations for the big day began years ago, Matt Bruning of the Ohio Department of Transportation told AFP.

He said the agency reached out to counterparts along the last major US eclipse, in 2017, and "one of the things that we heard resoundingly was it's never too early to start planning."

Despite those efforts, there will inevitably "be delays, there will be heavy congestion," he warned.

This year's path of totality is about 115 miles wide, wider than in 2017. It begins in western Mexico and arches up through the US cities of Dallas, Indianapolis, and Buffalo before ending in eastern Canada.

Many schools along the path will be closed or letting students out early, including in Cleveland and Montreal.

Several airlines have advertised flights scheduled to pass under the eclipse, while Delta has even planned two special trips along the path of totality, the first of which sold out in 24 hours, the company said.

NASA warns that only in the path of totality – and only during the few minutes of the actual totality – is it safe to look at the eclipse without eye protection.

Almost all of the United States will get to experience a partial eclipse, but UCLA astronomer Jean-Luc Margot says the trip to see the totality is definitely worth the hassle.

"If you have a 99% partial eclipse, that is a completely different experience than being in the path of totality," he told AFP.

Scientists have traditionally used eclipses to observe the solar corona, an outer layer of plasma that's difficult to study due to the Sun's bright light, Margot said.

New tools such as the space-based Parker Solar Probe have made such research less eclipse-dependent, but scientists will still be taking full advantage.

NASA recently highlighted several studies being planned for the eclipse, from effects on Earth's atmosphere and animal behavior to even human psychology.

"Eclipses have a special power," NASA Administrator Bill Nelson said recently. "They move people to feel a kind of reverence for the beauty of our universe."

Here's a handy guide on how you can safely watch the biggest astronomical event of the year!