SAN TERENZIANO, Italy - On a May afternoon, when the weather was unable to decide between sun and showers, the dedication of pork lovers here in this central Italian town was sorely tested. Again and again, rain arrived; the crowd scattered.

But again and again, as the sun returned, they poured back into the town square, appetites renewed for more porchetta: the aromatic, ancient whole pig roast that a crowd of hundreds had gathered to celebrate. It was the last day of Porchettiamo, a new festival devoted to porchetta, and a few showers were not going to keep them from the rare opportunity to taste a dozen different kinds of this beloved dish.

To make porchetta, a whole pig is deboned and gutted, then stuffed with garlic and herbs, and roasted in its skin until crunchy, juicy and insanely aromatic. (The head is left on, so when it is cooked, a whole porchetta looks like a pig in a brown sleeping bag.)

It is served sliced and stuffed into crusty rolls or between slabs of focaccia; because it is boneless, every slice has spirals of tender meat, lush fat and crunchy cracklings. As at a whole-hog barbecue in the United States, the goal is a mix of all three in each bite.

The dish is popular all over Italy as street food, almost always spotted at events like street fairs and weekly produce markets. Multiple sagras, or food festivals, are devoted to it every year. But Umbria fiercely guards its reputation as the birthplace of porchetta.

It is a simple dish, not a professional butcher’s masterpiece like the famous salamis from nearby Norcia, but it inspires great passions. “The idea came to me in a dream,” said Anna Setteposte, a co-founder of the festival. Its manifesto reads, “More than a festival: a declaration of love.”

Unlike most sagras, Porchettiamo gathers multiple producers from all over Italy, enabling porchetta partisans to taste, compare and simply gorge.

At one end of the festival, at the booth of Antica Salumeria Granieri Amato, founded in 1916, three generations of the Granieri family were handing children crunchy hunks of deeply bronzed skin. Their salumeria produces a strictly traditional porchetta, and is one of the last to still roast porchetta in a wood oven, for smoky flavor.

At the other end, the hip young chef Marco Gubbiotti of Cucinaa, a “gastronomic project” in nearby Foligno, handed out porchetta sandwiches stuffed with a confit of apple and fennel.

Some producers use fistfuls of garlic, others just pinches; some leave the liver in for the rich flavor it adds to the stuffing, others consider that bizarre; some perfume the meat with rosemary, while others maintain that only fennel pollen has the true flavor of Umbria.

Respect for food traditions was already entrenched in Italian culture when the modern values of eating locally, sustainably and transparently went global — partly via Slow Food, which was founded just a few hundred kilometers away. At Porchettiamo, the Umbrian reverence for pork, and passion for the deep culinary and agricultural heritage of the region, were on full display.

“The fennel is what makes it Umbrian,” said Barbara D’Agapiti, owner of Wine Link Italy, a guide to local food and wine. Fennel grows wild here, and its pollen has the refreshing whiff of dried sage, with notes of saffron, lemon and fennel seed.

To foreigners, Umbria and its food are often overshadowed by the high profile of Tuscany, which lies just to the west. But in Italy, Umbria is fondly called “il cuore verde d’Italia,” the green heart of Italy, for its fertile soil and ancient agricultural traditions. Pork from its green hills and deep forests has been prized since pre-Roman times.

Respect for food traditions was already entrenched in Italian culture when the modern values of eating locally, sustainably and transparently went global — partly via Slow Food, which was founded just a few hundred kilometers away. At Porchettiamo, the Umbrian reverence for pork, and passion for the deep culinary and agricultural heritage of the region, were on full display.

A whole pig is not practical unless you are feeding a whole town, but any boneless well-marbled roast with skin or a thick fat cap will do.

The key elements of the finished dish are juicy meat, soft fat and crispy crust. In modern Umbrian kitchens, porchetta has expanded beyond pork, so that “in porchetta” has simply come to mean boneless meat, rolled round garlic and herbs, and roasted.

Porchetta, the festival organizers say, deserved to be honored as food of the people, unlike luxury ingredients such as truffles, prosciutto and Parmigiano-Reggiano that typically command respect and attention from the greater food world.

“Street food is the food of the future,” said Antonio Boco, a co-founder of Porchettiamo. “Low-cost food, without boundaries, that makes many people happy: What could be more global than that?”