Alton Bay's famous ice runway will stay closed this winter due to unsafe ice conditions.

Paul LaRochelle is the state official in charge of the seasonal runway on Lake Winnipesaukee – the only one in the Lower 48 states.

He says the ice around the runway needs to be 12 inches thick to support maintenance vehicles and hundreds of aircraft.

This year, LaRochelle says warm weather has made the ice inconsistent – so he's keeping the runway closed.

"A lot of people say, ‘oh, they could have opened, it was cold this week and last week.’ It takes more than that,” he says. “It takes more than a few cold nights. It takes weeks for it to be a good thick safe ice."

He says the closure is in the name of “safety first.”

No full-scale vehicles should traverse the lake this season, he says, and snowmobilers and ice fishers should also use extreme caution.

The runway was also closed in 2016 and 2011, which LaRochelle says is as far back as his records go.

He doesn’t believe the closures are part of a long-term trend. It’s easy, he says, for localized weather conditions to create poor ice.

On the whole, scientists say New Hampshire winters are getting milder and less consistent as the climate changes.