Millions of East Coast residents received a “snow squall warning” on their cell phones Wednesday afternoon—confusing many who had no idea what the unusual weather term means.

According to the National Weather Service (NWS), snow squalls are bursts of intense snowfall accompanied by strong winds. The good news is that the bursts don’t typically last long, and the “squall” is typically over within three hours. Most last 30 minutes to an hour.

While short, snow squalls should be taken seriously. The NWS states that warnings are much like tornado or severe thunderstorm warnings, and can cause low visibility—making for dangerous travel conditions and accidents.

The New York City mayor’s office announced that a warning would be in place until 4:15 p.m. Wednesday.

“It will arrive quickly and powerfully, but it will not last very long. Be careful if you’re outside, visibility on the roads can decrease quickly,” the office wrote in a tweet.

The city’s emergency warning Twitter account cautioned residents about “blowing snow" with “wind gusts up to 30 mph” that could create “life-threatening travel conditions.”

NJ.com reports that 11 New Jersey counties received the snow squall warning due to an “arctic front” moving through the region. Four counties in Pennsylvania are also under the warning, news station WTAE reports.

To stay safe, the NWS recommended that residents consider alternate routes for travel or delaying any travel. When moving on roads, the agency advised individuals to “stay alert” for changing conditions along with slowing down and using low-beam headlights.