by Larry Copeland, USA TODAY

Ahh, that last holiday weekend of summer!

The Labor Day holiday has long marked the unofficial end of summer fun, and millions of Americans plan to hit the road Thursday and Friday for a final fling - at the beach, in the mountains or with distant family and friends.

But sitting in unexpected traffic jams can cut into that precious vacation time. Experts say travelers can reduce their chances of delays by avoiding certain places and leaving at certain times of day.

"Our advice would be to leave Thursday," says Jamie Holter, a traffic analyst with INRIX, a Kirkland, Wash.-based firm that provides traffic information from 10 billion data points daily. "But if you have to leave Friday, you want to arrange your trip so that you reach the chokepoint on your route before 1 p.m."

Gas prices are not expected to be a factor this year, so there likely will be plenty of other drivers approaching those chokepoints. INRIX says that with the exception of New York, holiday traffic in most places around the nation will be up 10% this year over Labor Day 2012.

Auto club AAA expects that 34.1 million people will travel at least 50 miles from home during the holiday, a 4.2% increase over last year. Of those vacationers, 29.2 million will go by automobile, a 4.3% increase over last year. Over the Labor Day holiday, which AAA defines as Thursday through Monday, the number of travelers is expected to hit a new post-recession high - an increase attributed to the improving economy.

Some parts of the U.S. will see even bigger increases, AAA spokeswoman Heather Hunter says. In the Pacific region, which includes California, Hawaii, Oregon, Washington and Alaska, the auto club expects a 5.7% increase in travel; the mountain region of Arizona, Colorado, Idaho, Montana, New Mexico, Nevada, Utah and Wyoming will see a 5.4% jump.

Across the nation, the busiest day for outbound travel is Friday, when 46% of holiday travelers head out. "Typically, Friday is a work day," Hunter says. "So you have traffic from people who are working and people heading out on vacation, so it could be very congested."

Her advice to Labor Day travelers: Leave early. "Travel in off-peak times typically helps," Hunter says.

Peter Kissinger, who's heading out Saturday morning for his family vacation in Rehoboth Beach, Del., plans to leave an hour earlier than usual on the trip he's taken for the past 10 years. "Everybody's going to be trying to get across the Chesapeake Bay Bridge," says Kissinger, head of the AAA Foundation for Traffic Safety.

Weather could play a role in some drivers' holiday travel plans.

"It looks pretty unsettled in the East," says Bruce Sullivan, senior forecaster with the Weather Prediction Center of the National Weather Service in College Park, Md. "A couple of disturbances are dropping southeast from the Great Lakes toward the Northeast and Mid-Atlantic regions. That'll produce a threat of showers and thunderstorms much of the period, especially as you get in toward the weekend."

In the West, he says, there's a holiday weekend "potential for showers and thunderstorms coming up from the Desert Southwest through the Great Basin. That area will continue to see some showers and thunderstorms. On the West Coast, there's a threat of precipitation in Washington and Oregon into the late weekend into Monday."

The central U.S. is likely to have the most travel-friendly weather as the Labor Day holiday weekend begins, Sullivan says. "There could be a few showers developing ... in the southern part of the central region."

During holiday holiday getaways, it's also a good idea to keep a cautious eye on the speedometer, says John Bowman of the National Motorists Association. "Obviously, as with all holidays, we would expect to see aggressive traffic enforcement across the country," he says. "You see police forces gearing up to do targeted enforcement operations. They typically focus on DUI, seat belt compliance and on speed traps."

For those making the return trip Monday, Holter advises hitting the road before noon. "If your expected departure time is 10 or 11 a.m., get on the road for an hour or two and then stop for lunch," she says. "Don't do lunch and then get on the road."

That's to beat the rush: According to AAA, the heaviest return day is Monday, when 43% will head back home. The auto club says 42% of holiday travelers will return home Tuesday or later. Many of them might find themselves caught in school-related congestion: Tuesday is the first day of school in many parts of the nation.

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Copyright 2013USA TODAY

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