Cellphones around the New York region began buzzing with an emergency alert from the National Weather Service at 3:30 p.m. on Wednesday: “Snow Squall Warning til 4:15 p.m. EST. Sudden whiteouts. Icy Roads. Slow Down!”

At about 4 p.m., phones were buzzing again. The warning had been extended until 5:30 as the squalls moved quickly across the region, creating potentially dangerous driving conditions in three states.

Just after the second alert was issued, the snow and wind — in gusts of up to 30 miles per hour — were swooping into New York City from the east, turning what had been a chilly, gray day into something more raw as the sunlight quickly faded away.

Among other things, the warnings prompted many people to ask: What is a snow squall?

The National Weather Service describes a snow squall as “an intense short-lived burst of heavy snowfall that leads to a quick reduction in visibilities and is often accompanied by gusty winds.”