Western Norway is experiencing a rare heatwave for early January, at a time when temperatures should normally be below freezing.
The highest temperature of 19C (66F) - more than 25C above the monthly average - was measured in the village of Sunndalsora.
This makes it Norway's warmest January day since records began.
While many were enjoying the warm weather, there are concerns that it is another example of climate change.
"It's a new record for warm weather here... People [have been] out in the streets in their T-shirts today," Yvonne Wold, mayor of the municipality of Rauma, who had taken a dip in the sea earlier in the day, told the BBC.
"A lot of people are usually skiing at this time. Not exactly much of that today," she added.
While the hot weather was a novelty, Ms Wold said there were concerns about the bigger picture of rising temperatures.
BBC forecaster Peter McAward said the previous January high in Sunndalsora was 17.4C.
It also breaks the record for any winter month (December to February) in Scandinavia, he adds.
While temperatures have been warmer in Scandinavia in December, he says the exceptionally warm day in Sunndalsora was down to its specific location.
"The main cause for the record-breaking temperatures at this particular site was from a foehn wind," he says.
Foehn winds are warm gusts that occur on the downwind side of mountain ranges.
The area also held the December (18.3C) and February (18.9C) Norway maximum records.