Rain, sleet or snow, everyone rushes compulsively to the grocery store for milk, bread and eggs. Many grocery store shelves are bare. It’s become an American snowstorm tradition.

But why? Stockpiling perishables is not always based in logic.

Dr. J. Kip Matthews, an Athens psychologist, said part of the reason is stockpiling behavior can give people a “sense of control in an uncontrollable situation.”

But Matthews believes other factors are in play particularly in Atlanta which experienced a crippling ice storm not too long ago.

The warmup will start this afternoon. Until then, stay off the roads. While conditions have improved on interstates, surface streets are still iced over and too hazardous for travel, the Georgia Department of Transportation said.

"When there is a perceived crisis (like a snowstorm), people tend to focus on getting their basic needs met including making sure that they have enough food on hand," Matthews said in an e-mail. "This behavior can be intensified when they go through an experience like that in Atlanta a few years ago when people were stuck on the road for 8 hours."

And there’s a herd mentality at play, too. If people see others flocking in droves to the grocery store, they may to follow suit.

According to AccuWeather, it appears that New Englanders can take credit for the buying up of milk and bread before storms. A monumental blizzard in 1978 that trapped many in homes for weeks gets at least some credit for the current tradition, according to AccuWeather.

READ: Up to date weather information for metro Atlanta

A year ago in January, if you headed to a grocery store, there was a good chance you were out of luck.

Why bread, milk and eggs? Maybe they are comfort foods.

For Matthews, he tends not to rush to the store for milk and bread unless there's a prediction of an ice storm and possible loss of power. Even then, he tries to make sure there's enough food that does not need to be cooked or refrigerated in the event the power goes out.

The need to for perishables was the inspiration for the French Toast Alert System, which according to its site is "joke to poke fun at the fact that, every time the weather gets cold (especially in certain parts of the country), stores seem to quickly run out of milk, bread, and eggs... which happen to be the ingredients for making french toast!"

Meanwhile, this mom of three wasn’t buying bread or milk during the anticipation of snow back in January 2017. She was buying wine in a box.

Tune into WSB for weather updates.

Atlanta snow: 1-4 inches expected, winter warning issued