With the threat of possible tornadoes touching down in the Garden State for a second day in a row, we asked an expert to clarify when exactly we should panic.

The National Weather Service issued a tornado watch for 10 counties in New Jersey on Wednesday and a tornado warning for parts of Hunterdon County Wednesday evening. (The watch remains in effect until 8 p.m. and the warning has since expired.)

But what exactly is the difference between a tornado watch and warning?

Tim Morrin, observation program leader with the National Weather Service in New York, said a warning means a tornado has been sighted by a trained spotter or local law enforcement or there’s evidence of a tornado on radar - such as rotating winds.

That means the hazard is happening or imminent, he said. Warnings are issued by local offices, like the National Weather Service in Mount Holly and usually last under an hour.

Watches, on the other hand, Morrin said, are issued by the National Weather Service’s Storm Prediction Center out of Oklahoma and span much wider areas like the size of an entire state or larger. Watches last for several hours.

“They are issued when conditions are conducive for the development of the hazard that the watch is for,” Morrin said. For instance, forecasters issued a tornado watch for parts of New Jersey on Wednesday, explaining that conditions were favorable for severe thunderstorms capable of producing isolated tornadoes with 70 mph winds.

A tornado watch is not as urgent as a tornado warning, but residents should remain alert as stormy weather arrives.National Weather Service

If your area is under a tornado watch.

Morrin suggests keeping a close eye on the forecast. Tune into the radio, TV or download a weather app on your phone that monitors weather statements from the National Weather Service. The key piece of information you’re looking for: A tornado warning.

If that happens, seek shelter.

“If you are in a structure, go to a lower level. If you are in a home, go to the basement or seek shelter in a small interior room,” Morrin said. If you live in a small apartment with no interior rooms, a closet in the hallway can work.

And if you’re on the road.

Morrin said it’s not recommended people be on the road during a tornado warning, but if you are, pull over in a safe, secure area if possible. “Cars get flipped around very easily," he noted. "Park and get to shelter.”

Karen Yi may be reached at kyi@njadvancemedia.com. Follow her on Twitter at @karen_yi or on Facebook. Get the latest updates right in your inbox. Subscribe to NJ.com’s newsletters.