That’s some proper prior planning.

A lost hiker missing for three weeks in the California mountains miraculously survived when she stumbled upon an unlocked cabin that had been left open by its owner for this exact situation — and was rescued just in time to celebrate her 28th birthday.

Georgia woman Tiffany Slaton found shelter at a closed resort in the eastern Sierra Nevada range after she was initially reported missing on April 29, authorities said.

A massive search for Slaton involved scouring more than 600 square miles at the Sierra National Forest, but it was Vermilion Valley resort owner Christopher Gutierrez who found her first this week.

He arrived at the venue Wednesday to prepare to reopen when he saw a front door slightly open and a pair of shoes.

“She pops out, didn’t say a word, just ran up and all she wanted was a hug,” Gutierrez said during a Wednesday evening news conference.

“It was a pretty surreal moment, and that’s when I realized who this was.”

He typically leaves the cabin doors open while the resort is closed during the off-season in case a wayward hiker needs a place to crash amid harsh weather conditions like blizzards.

“It’s mainly for people, just as this scenario played out, if they need to hole up in there one of shelter then it’s available,” Gutierrez said.

Slaton, who hails from Jeffersonville in the Peach State, told Gutierrez she survived for weeks solely munching on leeks before the resort owner fed her a peanut butter and jelly sandwich.

“It was a blizzard, and she pushed through that blizzard, and the first thing she saw was a cabin,” said Gutierrez. “And she held up in the cabin overnight … this girl was saved for the reason.”

The survivor was brought to a hospital and is in good condition besides dehydration, the Fresno County Sheriff’s Office said.

Her parents reported her missing late last month, and witnesses told the sheriff’s office she was last seen on April 24.

Two days before she was found, the sheriff’s office announced it was scaling back the search.

Bobby and Fredrina Slaton, her mom and dad, were losing hope when they received a phone call from none other than Tiffany as she was being taken down the mountain.

“She said, ‘Dad, I’m alive, and I’m sorry, but I’m alive and I wanted to call you and let you know I’m alive,’” an emotional Bobby Slaton said at the press conference.

As Bobby cried inside a store, Fredrina needed someone to hug.

“I grabbed somebody and said, ‘Can I hug you?’” she said. “And I did. I was crying and hugging.”

More information about Slaton’s incredible story of survival was not immediately known, including when or where her adventure began and how she ended up at Vermilion Valley Resort.

The sheriff’s office plans to eventually interview her for more details.

“Three weeks, it’s unheard of,” sheriff’s office spokesperson Tony Botti said. “It speaks to the tenacity that Tiffany has, that she’s a fighter.”

Slaton was rescued the day before her 28th birthday, People reported.

With Post wires