MASON CITY — The adventure began when Jonas Carlsson told his kids a story.

He recalled fondly as a boy when he and his brothers sometimes spent time during winters with their father building a snow igloo. Sometimes they slept in it overnight.

A light bulb went on.

“I should have never told them about it,” he said with a smile on Thursday. Once his sons, age 6 and 8, got the idea, “they wouldn’t take no for an answer.”

And so, earlier this month, Carlsson, 43, and his children put the plan into practice by constructing their own igloo, which measures 6 feet by 6 feet by 4 feet.

They made scaffolding with sticks for the igloo, which his sons referred to as a snow fort.

Four times this month, Carlsson slept in the structure with one of his four kids — a camping experience complete with sleeping bags, thermal pods and a backpack to seal the entrance.

With the entrance blocked, the temperature inside stayed warm enough to sleep through the night.

“It’s a good skill to have if you find yourself in the middle of nowhere,” Carlsson said. “It’s a good skill to survive in the woods if it would come to it.”

What took three hours to build took about 20 minutes for his sons Elias, 8, and Aaron, 6, to partially demolish, with Dad watching as they gleefully stomped down the interior on Friday.

“I am relieved to see this happening, because it means this is over at least until next year,” said Carlsso, a software engineer and stay-at-home dad.

His own father was an “outdoors-type” and engineer who tried to share these experiences with him, he said.

“That generation, they didn’t have that much time with the family,” he said. “When he did, he tried to do things like this.”

Next summer, Carlsson has promised his sons to build a tree fort in their backyard.

Will igloo-building become a family tradition?

“I suspect it will be,” he said. “They were planning for a bigger fort next year.

Transcription by Sharon R. Becker, March of 2016