It’s been three years since the temperature last dropped to minus 10 degrees in Portland.

Ten below was the frigid forecast for overnight Friday, but even that was nothing compared to 1971, when it got so cold that some recall Chebeague Islanders driving cars across frozen sections of Casco Bay to fuel up on the mainland, or 1934, when a ferry got stuck in ice and passengers walked the rest of the way to Peaks Island.

Forecasters expected the temperature in Portland to hit minus 10 Friday night into Saturday morning before warming up to 20 or above later Saturday. The last time Portland got that cold was Jan. 24, 2011.

“It’s certainly not common,” said National Weather Service meteorologist Chris Legro. “Generally speaking, it doesn’t happen every year, but we average maybe one or two (readings at that temperature) a winter when it does happen.”

The record low for Portland on Jan. 3 is minus 17, set in 1968, according to the National Weather Service. But that isn’t even among the 10 coldest temperatures recorded in Portland. Only temperatures of more than 20 below are on that list.

The record for the coldest reading ever in Portland was set on Feb. 26, 1943, when the temperature dropped to minus 39.

Then there was the winter of 1971.

Five of Portland’s 10 coldest days on record happened during that winter. Temperatures dropped to minus 22 or colder and stayed there for days at a time. Parts of Casco Bay froze over enough for people to make their way from Chebeague Island to the mainland without a ferry, said Donna Damon, an islander who is president of the Chebeague Island Historical Society.

Chebeague is about a mile from Cousins Island, which has a bridge to the mainland, and nearly three miles from the mainland in Falmouth.

Damon remembers a handful of times when parts of Casco Bay froze over, and has heard many stories dating back to the 1870s about islanders being iced in.

In a diary from 1876 that was donated to the historical society last year, one islander describes a 12-week period when the water between Chebeague and Cousins islands was frozen solid.

“They could get teams of horses back and forth between the islands,” Damon said. “In 1918, (the bay) froze all the way to Bates Island (from Chebeague). Someone built a house on Bates using materials they took out over the ice.”

Bates is a small island about two miles east of Chebeague.

That winter, Damon’s mother, then 6 years old, walked about a mile from Chebeague to Cliff Island with her parents to visit a relative, she said. A couple from the island got married in Portland, then walked back to Chebeague, stopping at each buoy for photos.

“That was a big year,” Damon said.

In 1902, a doctor was called in from racing his horses on the frozen bay – in March, no less – to attend to a birth, according to Damon. Back in those days, islanders would walk on Casco Bay in search of places to go clamming, she said.

Newspaper clippings from 1933 and 1934 describe a Casco Bay frozen so hard that people drove cars between Chebeague Island and Falmouth, reportedly following the ice that formed around Littlejohn and Cousins islands.

In February 1934, the Casco Bay ferry Emita got stuck in the ice, and passengers had to walk 200 yards across the bay to Peaks Island.

In 1968, Damon had her own harrowing experience when the boat that ferried students to and from the mainland for school got stuck in ice near Chebeague Island. The students, warmed by a small coal stove, heard the wooden boat creaking as the captain worked to free it and get to the island.

Damon said the last time she remembers parts of Casco Bay freezing was in the early 1980s.

“From what I know, this is the longest period of time that it hasn’t frozen over at least once during the decade,” she said.

The National Weather Service in Gray doesn’t keep track of how often Casco Bay has frozen, but meteorologist Legro said the conditions in Portland this winter aren’t the kind of extreme cold that’s needed to freeze salt water.

“The biggest condition you would need would be sustained cold,” he said. “You need several days of single digits, with well below zero at night, to see any sort of ice accumulation in the bay.”

Gillian Graham can be contacted at 791-6315 or at:

ggraham@pressherald.com

Twitter: @grahamgillian