Roads in the Uusimaa region and in the south of the country were also affected, with conditions on minor roads being the most dangerous.
The South Savo and South Karelia regions were both hit by snowstorms overnight, with around 20 cm of snow falling around the town of Mikkeli.
Heavy snow south of Joensuu has also resulted in extremely poor driving conditions in the region. Towards the south of the country the snowfall extended as far as Mäntsälä. The current area of low pressure is moving eatwards. Forecasters say local showers of sleet or snow can be still expected. Some may be heavy in places. However, most of the snowfall will die out on Saturday.
Although no serious accidents have thus far been reported, the Institute warns that particular care must be taken by drivers still using summer tyres.
There was very heavy traffic between the towns of Varkaus and Joensuu overnight. Niinimäki was also the scene of long queues of lorries on Highway 23 as a result of the slippery road conditions.
As many as 20,000 households faced power cuts on Friday due to the bad weather. However, power has been restored during the day.