A powerful polar vortex is currently freezing the Midwest but the Northeast and nearby regions are now facing another winter threat from Mother Nature: snow squalls.

Snow squall warnings were issued across several major cities in New York, New Jersey, Pennsylvania Wednesday afternoon. A snow squall, also known as a "whiteout," refers to a burst of snow that occurs suddenly (and without warning) that is accompanied by strong gusts of wind.

"By definition, a squall is a sudden violent wind, often accompanied by rain, hail or snow," Accuweather previously described in a blog post, adding that they're like "wintertime thunderstorms."

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They're mainly witnessed during winter months but can happen any time — typically between October and April.

"They are often small in size, but they can bring intense snowfall, just as thunderstorms bring intense rainfall to a small area," the weather site explains. "These wintertime showers form when the air near the ground is much warmer than the air aloft. First, towering clouds develop. Next, that moisture is released in the form of snow."

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The sudden "blizzard-like" snowstorm is dangerous for drivers, as it impacts visibility.

The dangerous weather phenomenon is being blamed for causing a massive pileup in Reading, Pennsylvania, Wednesday afternoon.

Dozens of cars were involved in the chain-reaction crash on Route 222 near Wyomissing. About an hour later, a second pileup was reported on Interstate 78 near Hamburg, about 30 miles northeast of the Wyomissing crash, causing minor injuries.

The Associated Press contributed to this report.