CHICAGO — Starting Saturday, possibly hundreds of Chicago drivers will return to where they parked their cars the night before only to find the vehicles have mysteriously disappeared.

It's like that every Dec. 1, when Chicago's infamous annual Winter Overnight Parking Ban goes into effect. Every day between 3 a.m. and 7 a.m. until April 1, city tow trucks will spirit away vehicles parked along 107 miles of Chicago's main arterial streets to one of Chicago's auto pounds.

Department of Streets and Sanitation spokeswoman Anne Sheahan said her department has had boots on the ground since Monday reminding drivers of the winter ban’s imminent return by placing fliers on the windshields of cars parked along streets affected by the ban.

"Our goal is to have the season start with no tows," Sheahan said. "No one wants to come out and find their car has been moved. We're trying to do our best to see that people don't get ticketed and towed."

Getting towed in violation of the winter ban is expensive. Counting the $50 ticket and the $160 in tow fees, drivers will fork over a minimum $210 at the auto pound to get their car back.

Sheahan strongly advised motorists who park along winter ban streets to think of the ban as starting Friday night, not Saturday morning.

"Remember, when you go to bed Friday or park your car Friday night, the ban will take effect overnight," Sheahan said. "We want to stress to people the ban will be in effect at 3 a.m."

The genesis of the winter parking ban was the number of abandoned cars during the Blizzard of 1967. With so many cars clogging main arterial roadways during that snowstorm, snowplows were unable to do their jobs effectively, Sheahan said.

The solution has been to keep these crucial routes open overnight, no matter the weather, snow or no snow.

"We're not out to get people and not doing this to make parking difficult for people," Sheahan said. "Historically, the city has encountered major issues clearing these major streets in order to create a safe driving atmosphere for residents. If the streets are clear, we can do our job and people can get to work."

While the first night of the winter parking ban always sees more vehicles towed away than any other night during the four months the ban is in place, the first night of this year's winter ban could see city tow trucks hooking up more cars than in past years.

That's because Dec. 1 falls on a weekend this year. Based on historical data from Streets and Sanitation, 50 percent of all cars towed in violation of the winter ban occur on just two days — Saturdays and Sundays.

Sheahan says there are probably a lot of factors at work to explain this, including drivers who are out on a weekend night parked in an unfamiliar area.

In addition, total tows for violating the winter overnight parking ban were up 7 percent last season, rising to 9,191 from a total 8,582 tows in 2010-2011.

All these factors could mean a lot more drivers will be surprised to find their vehicles missing than the 188 cars towed last December.