In a season traditionally associated with ice-skating, snowball fights and mulled wine in wintry Europe, birds are chirping, flowers blooming and fake snow covering Alpine ski slopes in one of the warmest Decembers on record.
In Finland, normally one of the coldest places on Earth with December temperatures in the minus, the mercury hit a record 10.3 degrees Celsius (50.5 degrees Fahrenheit) in the capital Helsinki on Sunday.
Temperatures in the teens were recorded in Sweden and Estonia, while London's St James' park measured an astonishing 16.9 C on Sunday.
Even glacial Moscow has been chalking up above-zero thermometer readings.
"The average temperature on Monday (5 C) is almost 12 C above the norm for the season (minus 6.5 C)," weatherman Nikolai Terechonok told AFP.
None of the capital's 1,200 natural ice rinks have opened this winter and the artificial rink on Red Square was closed Monday for "technical" reasons.
"It is not an ice rink any more, but a beautiful pond," said an attraction employee.
In the Italian Alps, ski stations have had to resort to artificial snow, cherry blossoms have been spotted in Dresden in Germany, and daffodils are flowering in England.
Last week, the Royal Dornoch golf range in Scotland tweeted: "The mowers are back out to cut greens in mid December!"
As clement weather abounds, many may wonder: Is global warming behind it all?
It is hard to know with certainty, experts say, but climate change is unlikely to be the sole cause.
"It is nothing new to have such a big change from one year to another," Frederic Nathan of the Meteo-France weather office told AFP, pointing to natural variability.
Previous record-warm Decembers occurred in 2000, he said, and in 1934—long before man-made climate change became an issue.
Climatologists are loath to attribute a specific weather event, such as an exceptionally warm year, to global warming—but do predict that people in northern Europe will become accustomed to these type of warm winters.
Parts of the United States and Canada too, have been experiencing an unusually balmy winter, while in the southern hemisphere Australia has been battling heatwaves and bushfires and southern Africa severe drought.
US government scientists say the world shattered yet another heat record in November, and 2015 would likely be the hottest year in modern history.
Europe experienced its warmest November since 1910.
The overall trend, scientists say, is due to climate change, whereby emissions from burning fossil fuels accumulate in Earth's atmosphere and trap heat.
- Still autumn? Already spring ?-
But in some parts of the world, the El Nino phenomenon, particularly strong this time around, is helping drive up temperatures.
Britain's Met Office last week said the global mean temperature for 2016 was expected to be about 0.84 C warmer than the 1961-1990 average, even higher than the 2015 prediction of 0.64 C.
"This forecast suggests that by the end of 2016 we will have seen three record, or near-record, years in a row for global temperatures," Adam Scaife, head of long-range prediction, said in a statement.
The Met Office said it did not expect the run of back-to-back record-breaking years to continue indefinitely.
"But the current situation shows how global warming can combine with smaller, natural fluctuations to push our climate to levels of warmth which are unprecedented in the data records," it said.
On December 12, 195 nations signed a pact to limit average global warming to "well below 2 C" over pre-Industrial Revolution levels, and aim for 1.5 C in a bid to "significantly reduce the risks and impacts of climate change".
Some fear it could be too late for certain holiday pastimes that rely on natural snow or ice.
"Ski? Ski where?" lamented Natalia Afanassieva, who runs a ski resort near Saint Petersburg.
"We understand nothing. Are we still in autumn or already in spring?"
Explore further: Another heat record means 2015 likely to be hottest ever (Update)