Water situation snapshots
Snow situation 30.3.2023
Snow in the entire country – less than usual in some parts of Southwest Finland
In Southern and Western Finland, the snow load is mostly 40–80 kg/m2 and in Central Finland and in the southern parts of Eastern Finland and Northern Ostrobothnia 80–120 kg/m2. In Kainuu, the snow load is 150–220 kg/m2, the Paljakka hill in Hyrynsalmi being the snowiest place. In Lapland, the snow load varies between 100 and 180 kg/m2.
Air-supported structures are already at risk of damage and collapse with a snow load of 30 cm (50–60 kg/m2).
The Finnish Environment Institute and the Finnish Safety and Chemicals Agency warn of the risks of snow load on roofs of large halls (press release 21 January 2022, available in Finnish)
Snow course observations are made once a month and twice a month during the snow melting period.
When should I push snow off the roof?
A roof snow load may damage the structures of large halls, in particular, which is why the snow should be pushed off the roof in time. A property owner must also ensure that snow and ice cannot slide off the roof and hurt passers-by. However, you should not take it upon yourself to climb onto the roof of a residential building to push down the snow.
Halls with a large frame
Buildings and halls with a large frame are high-risk sites in terms of snow loads. Any hidden structural defects in such halls usually come to light when the snow load reaches around one hundred kilograms per square metre. Even a layer of 50 centimetres of snow should be removed from the roof, but this job should be entrusted to professionals.
Air-supported structures that are held up by internal air pressure are no match for the weight of snow, and they may collapse under a layer of just 20 centimetres. As 20 to 30 centimetres of snow can accumulate over a short period of time in Finland, these structures are unsuitable for the winter conditions in our country.
The roof structures of private houses and high-rise residential buildings can carry a large snow load, usually with no risk of collapsing, whereas icicles falling off the roofs are a particular hazard. To avoid putting your or other people’s safety at risk, you should never climb up to a roof without proper safety equipment.
Fun facts about snow?
Snow squeaks at low temperatures
At extremely low temperatures, snow crystals have a high number of branches, and the fragile crystals break easily when you walk in the snow. This makes a squeaking sound under your feet. A seasoned winter hiker can determine how cold the temperature is by listening to the different tones of this sound. In mild weather some of the branches melt under your footsteps, and water acts as a lubricant between the crystals, reducing the noise.
Snow has no colour
While snow may look white, this is only the effect of reflections, and it actually has no colour. All visible light wavelengths are reflected equally from the snow surface, making snow look white. In clear weather snow can take on a blue hue that is a reflection of the blue sky. Wet snow reflects light less well, and this makes it appear grey.
The weight of snow varies
Hard-packed, wet snow may be up to four times as heavy as dry, newly fallen snow in cold conditions. While snow compacts in mild weather, this does not increase the roof snow load. If it rains, however, the load may increase as the snow absorbs water. There is little or no evaporation from snow.
Snow forms layers
WWhen snow builds up on the ground or on a roof, its quality is rarely consistent. It has different layers depending on the conditions in which it fell, and the layers are also affected by any milder intervals. The bottom layers are also compressed by the weight of the top ones.
Snow helps you keep fit!
Outdoor exercise in winter is highly significant for public health in Finland. In particular, cross-country skiing is a versatile sport for improving stamina. The number of people who go skiing and take part in other winter sports grows in those winters when enough snow falls even in Southern Finland. Children also love spending time outside and playing in the snow.