HALLOWELL — Years spent working as a merchant mariner, river pilot, port captain and harbor master give Arthur Moore perspective on the freezing of the Kennebec River.

This winter, he’s “99 percent sure” this is the latest the river has been open since at least the 1950s, and he has photos as evidence.

“This is the longest spell the river’s been open since 1949,” said Moore, 91, of Hallowell.

He offers a photo from Jan. 10, 1949, of an oil tanker on the river in Hallowell. Another photo shows the tanker going through the Richmond/Dresden Bridge.

Most years, he said, the oil deliveries to the riverside depots had to be completed before Dec. 15, since the ice would form at some point between then and Jan. 1.

He remembers, too, piloting a tanker up the Kennebec and getting stuck on ice at the north end of Swan Island, almost at the bridge, in late December 1955.

When the ship was chipped out of the ice with pick poles and some assistance from the tide, he refused to take it north again, telling the captain it was time to return to Bath.

On Friday, the river was flowing freely in Augusta, Hallowell, Gardiner, Skowhegan and Fairfield, tucked back into its banks after coming close to reaching flood stage a few days ago.

Sean Goodwin, director of Kennebec County’s Emergency Management Agency, said Friday that he would have anticipated more river ice in December. Instead, “nothing.”

But he pointed to some of the single digits in the temperature forecast for the upcoming week.

“We’re going to see some ice form again,” he said.

On Friday, he saw frazil pan ice.

“It looks like big lily pads,” he said. However, no ice was forming along the riverbanks to anchor it.

Gregory Stewart, supervisory hydrologist with the New England Water Science Center, of the U.S. Geological Survey, said Friday that the Kennebec had an ice cover of frazil or slush ice in early January in Augusta.

“The Kennebec has been open many times over the winter months,” he said, referring to what some would call the January thaw.

Preventing much ice cover this season he said was the heavier-than-usual rainfall in November and warmer weather in December.

Stewart said three factors affect ice formation: air temperature, water temperature and river flow.

“The higher the river flow, the harder it is for ice to form,” he said. “It’s also challenging because of (dam) regulation on the Kennebec River.”

Increasing the river flow in the headwaters can force ice to move, he said.