Thousands of Wegmans superfans flooded the cult-favorite grocery store’s first Big Apple outpost Sunday — including some who began lining up in the pouring rain at 4 a.m. for its grand opening.

“I’ve been waiting for this my whole adult life,” said Kimberly Ciaccia, 40, of Brooklyn, who arrived at the new store in the Brooklyn Navy Yard well before the crack of dawn.

“I had tears in my eyes. I was so excited,” she said of opening day.

The shop opened at 7 a.m. to cheers from those standing in a line that had already wrapped around the sprawling store.

At least 3,000 shoppers had made the pilgrimage to the 74,000-square-foot store by noon, said an employee of the Rochester, NY-based grocery chain.

Mallory Milligan, a nurse who lives in Astoria, Queens, said she and a pal arrived at the store “immediately” after her overnight shift.

“The opening day has been written on our calendar for over a year. We knew we were coming,” Milligan told The Post.

But she said that she came prepared with a game plan to conquer the store’s aisles, which were bursting with Wegmaniacs, thanks to a store app.

“We have it all planned,” Milligan said. “I have the app, and you can see which aisles the food you want is on.”

Shopper Rashida Shabazz, who took on the fracas with her dog, Wishbone, made some lifelong friends in the chaos.

“I made a new best friend here from Wisconsin in the produce area,” said the 70-year-old retiree, who spent the night at her sister’s home in Brooklyn to arrive early for the opening.

But Shabazz said that she wouldn’t hesitate to make the hour-plus commute from her Upper Bronx apartment.

“The quality of produce and food here is the best,” Shabazz said. “Do you know the potency of this? My body will say thank you!”

But other customers didn’t have the stomach for the grocery pandemonium.

“We got some groceries today, but it was chaos,” said Rona Salomon, who arrived with her two young daughters. “We couldn’t go through all of the store because they don’t have carts for kids yet.”

The grocery chain insisted that it “seems like everyone is having a good time” despite the mayhem.

“Nothing chaotic has happened yet,” Wegmans rep Tracy Van Auker told The Post. “You walk through the aisles, and you encounter a lot of folks, but so far, it’s running smoothly.”