Many parts of Finland see zero hours of sunshine in December

Meteorologists say inversion is causing cloudy, overcast skies.

A Christmas tree lights up grey skies around Turku Cathedral this month. Image: Saana Sjöblom-Hasselblatt / Yle

Over the past few weeks the weather in large parts of Finland has been characterised by dense, low-hanging clouds--a condition meteorologists say is caused by inversion.

"Normally the air cools as it rises in the atmosphere, but now we’re in an inverted situation where warmer air is higher up," explained meteorologist Antti Kokko from the Finnish Meteorological Institute (FMI).

Kokko said inversion happens when a parcel of warm air forms a cap at high altitudes. This in turn causes warm air closer to the surface to spread sideways and form clouds.

0.1 sunlight hours in Seinäjoki

When inversion happens, it can take some time for it to clear up. That said, many parts of Finland haven’t seen much of the sun this month.

"Maarianhamina recorded 0.2 hours of sun and Seinäjoki 0.1 hours so far in December," Kokko explained.

Seinäjoki in western Finland usually gets an average 18 hours of sun in December, which means the city should have seen around nine hours by now, according to Kokko.

Southeastern Finland has had the most sun this month, with Kotka and Lappeenranta clocking between 14 and 15 hours so far.