(CNN) -- A resounding boom over Tucson, Arizona, roused residents from their dinner tables Tuesday and had them pointing up to the sky.
With the largest meteor shower of the year around the corner, the heavens seemed to be giving them a sneak preview. A whopper of a fireball roared over their heads and exploded, rattling their houses.
A dash cam captured it on video as it vanished in a bright blaze.
The spectacular annual Geminid meteor shower kicks into high gear Thursday night, NASA said, and people around the world will be able to enjoy it.
Some of its meteors have already been dashing through Earth's atmosphere. The agency recorded nine of them Tuesday night.
But the Tucson meteor did not appear to be one of them, said NASA meteor expert Bill Cooke, who analyzed the flying space rock after two NASA cameras in Arizona recorded it on video.
Traveling at 45,000 mph, it was too slow.
"A Geminid moves at 78,000 mph," he said. And the direction it came from was not typical for a meteor from the big shower.
The Arizona fireball was just one of the handful of "sporadic background" meteors that whiz through the atmosphere every day.
But this was a big one, Cooke confirmed. It weighed about 100 pounds and was about 16 inches thick. It made quite a bright flash, as it burned up in the atmosphere.
Even with 100 to 120 meteors per hour coming down during its peak on Friday and Saturday, the Geminid shower now has a tough act to follow.
Astronomer Tod Lauer heard the blast but did not bother to look outside.
"We were eating dinner and heard a good bang that rattled the roof of our house. I dismissed it as a sonic boom," he posted to Facebook.
He realized it had to be more than that, when a local TV station phoned the scientist, who studies images from the Hubble Space Telescope, to ask him to explain what had happened.
Frantic eyewitnesses across the state called local news outlets to report what they saw.
The explosion shook Tony Kubrak's house, too, he told CNN affiliate KGUN, which received a flood of calls and hundreds of posts to its Facebook page.
Kubrak went outside to check it out.
"I see this tremendous, white, bright light in the western sky. And it was just ... it was absolutely enormous, I couldn't believe it."
Others took to social media.
"Did y'all see the meteor that flew above Tucson? Crazzzzy. That was toooo craaaazy!" Tucson resident Eric Gomez posted on Twitter.
People around the world can share some of the thrill that bedazzled Arizonans until at least Monday, NASA said. The Geminid meteor shower will be "rich in fire balls."
"Of all the debris streams Earth passes through every year, the Geminids are by far the most massive," he said. "When we add up the amount of dust in the Geminid stream, it outweighs other streams by factors of 5 to 500."
NASA calls it the 900-pound gorilla of meteor showers.
Most meteor large showers are caused by comets, which are loosely put together with lots of debris in tow that fly into the atmosphere -- but not Geminid.
An asteroid large space rock named 3200 Phaethon flings the stardust that makes the sparkling magic.
Of all the named asteroids, it is the one that flies closest to the sun, Cooke said -- 2.5 times closer than the planet Mercury.
It's a bit of a mystery why 3200 Phaeton is flying with so much debris, Cooke said. He thinks perhaps it was produced by a collision eons ago with another asteroid.
Geminid contains the name of the constellation Gemini, which is the direction the meteors will be coming from.
They can be viewed well starting at 11 p.m., but Cooke recommends waiting until an hour before dawn, "if you can stand the cold." That will give the bright moon time to set and allow the heavens to darken.
Don't use a telescope or binoculars. He recommends lying flat on your back in a sleeping bag so you can take in as much of the sky as possible.
He won't be joining you, but will wait until morning to watch video recordings captured by NASA's cameras -- for comfort's sake, he said.
"I'm too old to freeze my rear off anymore."
CNN's Mayra Cuevas contributed to this report.