Image: Saana Antikainen

Shortly after midnight, this winter's new cold record of -41.7 degrees Celsius was set in Muonio, Finnish Lapland. It was nearly as chilly in the village of Naruska in Salla, where thermometers showed -41.4.

A day earlier, the record was snapped twice in Finnish Lapland.

According to the Finnish Meteorological Institute (FMI), thermometers sank to -38.7 degrees Celsius shortly before 7 am at Nuorgam in the northernmost municipality of Utsjoki. Just after noon that record was bested by the village of Väylä, slightly further south in Inari. There the mercury plunged to -39.8.

Freak electrical storm

Meanwhile the FMI reports a weather anomaly: a freak winter thunderstorm over parts of Espoo and Kirkkonummi early Wednesday, with one bolt of lightning even striking Kirkkonummi's southern Porkkala peninsula around 12.30 am.

Meteorologist Ari Mustala says such an event may happen once per winter somewhere in Finland on average, usually on the coast or at sea.

"Usually winter lightning occurs because the sea is still warm. The Gulf of Finland has not frozen yet, so it can create powerful updrafts in certain circumstances," he tells Yle.

Health hazard for risk groups

The FMI has issued a warning of severe cold throughout the country through Friday, with readings of -40 possible in the far north. That, incidentally, is the point where the Celsius and Fahrenheit scales cross.

The FMI notes that the deep-freeze temperatures may cause health problems for those in risk groups. They also coincide with an unusually early, aggressive flu epidemic that has already killed at least 21 patients in Finland.

On Thursday, subzero temperatures in the double digits are forecast throughout mainland Finland. The west coast will be mildest with readings of around -15, while the Åland Islands will bask in a relatively mild -7.

On the plus side, skies should be mostly clear, with a chance of light flurries along the west coast. And road and sidewalk conditions are expected to be normal throughout the land.

Those planning sea cruises may want to reconsider. Along with the frigid cold, there are also warnings of gale-force or near-gale winds, with rough waves of over four metres on most sea districts.