Exceptionally heavy snow loads piling up on rooftops have caused accidents and alarm across Finland in recent weeks. Large industrial buildings and sporting arenas with flat roofs have been particularly worrisome. On 6 March a floorball hall was closed in Helsinki due to danger of the roof collapsing under heavy snow. In late February two people were injured when a steel-framed sports hall collapsed in Järvenpää. Accidents involving snow and ice sliding down from rooftops have claimed lives and injured many.

According to the environmental administrator SYKE, snow loads will keep growing. From 1 March onwards the snow load in Southern Finland will increase by roughly 15kg/m2 under average weather conditions, although once every 10 years an increase of as much as 40kg/m2 can occur. In the northernmost reaches of Lapland the increase can vary from an average of 30kg/m2 to as much as 70kg/m2.

Contrary to popular belief, the weight of the snowpack does not automatically increase as daytime temperatures rise above zero, unless rain or sleet add to its total mass. Instead, thawing conditions make the snow and ice masses more liable to slide down from roofs.

MATTI KOSKINEN - HT