The Art Shanty Projects were moved off the ice to the shore of Minneapolis’ Lake Harriet last month because of ice-quality worries. (Max Haynes/The Minnesota Star Tribune)

The weekend's mild temperatures melted hopes of winter fun, as several ice-dependent festivals and fishing derbies were called off over ice-safety concerns.

The Fire and Ice festival in Plymouth, Chanhassen's February Festival, the Maple Lake Fishing Derby and the Chaska Fire Department's fishing contest were among those canceled, while the Art Shanty Projects last month were moved off the ice to the shore of Minneapolis' Lake Harriet over ice-quality worries.

Last week aside, Minnesota has seen a mild, snowy winter, said National Weather Service meteorologist Mike Griesinger, which has made for weaker-than-usual ice.

"This has kind of been a nightmare of a year for making lake ice," he said.

The problems started with milder weather and frequent snow in December, Griesinger said, followed by milder-than-usual temperatures and more snow in January. Even if temperatures in the mid-20s, like those the Twin Cities saw through most of January, are technically below freezing, ice formation is slower and the ice isn't as strong.

Though ice varies year to year, the U.S. Environmental Protection Agency notes that since the early 1970s, the number of frozen days on the Great Lakes has declined. The agency tracks ice on the Great Lakes as an indicator of climate change and predicts fewer frozen days as the climate warms. Compared with 50 years ago, according to the agency, the lakes are frozen between eight and 46 fewer days; the decreases in frozen days on Lakes Ontario and Superior are considered statistically significant.

Sustained cold makes for the best ice: Think back to the winter of 2013-14, Griesinger said, when it was cold enough to freeze much of Lake Superior.

"Cold like that is what you want," he said, cold below zero or just a few degrees above, for weeks on end, and before too much snow falls.

"If you have open water still, that's ideal," Griesinger said. "Then that open water will freeze, and it will freeze hard, clear ice. That's strong ice."

But that's not what Minnesota lakes have had this year. Instead, the ice formed over the winter so far has a weaker structure, almost like crushed ice.

By mid-January, event organizers started canceling or modifying events set to bring lots of people to imperfectly frozen bodies of water. The Art Shanties moved on shore, and several winter events were postponed in January.

Snow blanketing the lakes meant the water was insulated from last week's cold air, so the arctic chill didn't get a chance to work its magic last week.

Then over the weekend, disaster — at least for ice anglers and pond hockey players. The Arctic air mass drifted away and temperatures crept toward the freezing point. In the Twin Cities, Saturday's high was 28 while Sunday was on track to hit 30. In western Minnesota, near the South Dakota border, Griesinger said it was close to 40 degrees.

The St. Paul Winter Carnival celebrated Saturday night's Vulcan Torchlight Parade on schedule, with no need for ice — the parade symbolizes the coming end of winter in carnival lore.

Though the National Weather Service forecasts more cold after Valentine's Day, Griesinger said it might be too late to form really good ice as the days get longer, the sun gets higher in the sky and spring draws just a little nearer.