FOXBOROUGH, Mass. – The traffic was already bumper to bumper, two lanes wide, and moving slowly but steadily on Route 1 as the snowflakes fluttered down lightly but steadily late Sunday morning.

Church services? Well, in a way, yes, for this is a religion to the thermal underwear-clad thousands packed into their SUVs, pickup trucks, and cars – roughly every fifth vehicle sporting a gas grill in the back – along with enough food, beverages (alcoholic and non), condiments, napkins, plates, and cooking supplies to stock a grocery store.

It’s 41/2 hours before kickoff for the New York Jets-New England Patriots game, but the veterans are already out in full force, cold temperatures and snowfall be damned. There are tents to be erected, fires to be lit, food to be cooked, and people to see. It’s football time in Foxborough.

The license plates read like a New England road map guide: Massachusetts, New Hampshire, Rhode Island, and Conecticut are the most plentiful, but it’s not too hard to find Maine or Vermont along with much less plentiful plates such as Virginia, Michigan, and Nova Scotia. On this day, another plate which usually falls into the “hard to find” category is decidedly not: New York.

“Yeah, we drove over from New Rochelle this morning. It took 31/2 hours to get here,” said 31-year-old New York Jets fan Domenic Gaglianese, who’s had a tough year with his 2-9 Jets besieged by injuries and his brother Tommy being a longtime fan of the unbeaten Indianapolis Colts. “It was pretty bad, but we didn’t have any close calls.”

Gaglianese and two friends drove to Gillette Stadium to see the Patriots host the Jets, an AFC East rival. These hard-core fans have been to San Diego, Philadelphia, Washington, and Miami to see games. A snowy road trip to Foxborough wasn’t about to faze them, even with a Patriots fan in the back seat.

“We took the muzzle off him an hour or so ago,” said Andrew Cafaro, 25, referring to Mark Puleo, a Medford, Mass., native now living in Newburgh, N.Y.

Puleo’s used to suffering the presence of Jets fans. His wife is one.

“I met her in school in Boston, and when she had a baby, she wanted us to move to New York to be closer to her family. She used to always harass me about how bad the Patriots were early on, but now I get bragging rights,” Puleo said.

That doesn’t mean he gets TV rights, however.

“I go out and watch the games most Sundays and she stays home because I don’t have DirecTV,” Puleo added. “If I stayed home, I’d have to watch the Jets and that makes me puke.”

Unless it was from eating or drinking too much, there wasn’t much of that going on in the vast tailgating section at Gillette Sunday.

Everything from standard fare like hot dogs, hamburgers, and chili to more exotic dishes featuring chicken, shrimp, lobster, steak, and even lamb or venison was being cooked over open flame, burning coals, or electricity by thousands of cookout chefs.

While others go for variety, Bill and Janna LaFond and friends – all from Portland – like to keep things somewhat familiar. They go with marinated steak tips and sausages as their main dish.

“We usually come down once or twice a year and it’s a lot of fun. We enjoy the food and the people,” said Chris O’Brien, who made the 21/2-hour trip from Portland with the LaFonds Sunday. “It’s a great atmosphere, no matter how the weather is.”

Longtime football fan Janna LaFond, a Winslow High School graduate and former Black Raiders varsity cheerleader, couldn’t agree more.

“If I could get some season tickets – ahem,” LaFond said with a wide smile and her eyebrows raised in the direction of her husband, “I would do this every week!”

As it is, the LaFonds come down at least once a year via tickets Bill gets through his business, LaFond Roofing.

It’s easy to tell the accomplished experts from the rank amateurs and less-serious tailgaters at Gillette. The first things that separate the hardcore wheat from the casual chaff are the 3-by-5-foot flags flying from poles erected on the tailgating sites. Another clue is the location and type of vehicles brought by the tailgaters. No compact cars or sedans here. It’s SUV, pickup, or tricked-out van, baby!

Then there are the upper crust of the tailgating elite. Old hands at it such as 53-year-old John Lynch of Sturbridge, Mass.

“I’ve been a season ticket holder for 30 years now and I’ve been tailgating now for the last 15,” said Lynch, owner of Boston Closet Co. “When we started out, it was bologna-and-cheese sandwiches, or sometimes we’d switch if my friend brought salami.”

The tailgating trade has really seen a transformation in recent years, and Lynch has been here through it all. No more bologna and cheese or even dogs for him. His operation is first class, all the way.

“We came down with about five cars and 20 people and we met up with another 10 from Connecticut,” Lynch said. “It’s a little larger than our usual group.”

But no less elaborate.

Lynch and lifelong buddy George Doyle of Somerville, Mass. – who grew up two streets away from syndicated afternoon talk show host and Portland native Howie Carr – shoot the works at these things: collapsible shelters with roofs, plenty of tables and chairs, heaters, gas grills, a 32-inch TV set, an all-weather surround sound system, and a menu that would make some restaurants proud.

“Well, today we have Cajun shrimp, marinated chicken, beef tenderloin, scallops, casseroles, and all kinds of appetizers,” Lynch said while munching a shrimp.

If that’s not enough, team Lynch/Doyle brings along a satellite TV system and an iPod to program their TV and stereo systems, respectively.

The theme is the same for most tailgaters – old or young, experts or novices, serious or casual – when asked what the most important rule of tailgating is.

“You always bring a lot of clothes, no matter what the weather is like when you leave the house,” said Brian Grochowalski of South Hadley, Mass. “You throw everything in the truck because you never know what you’ll need later and it’s better to have too much than not enough.”

Until Martha Stewart takes up tailgating, that advice is “a good thing.”