Thermal spring began in Helsinki on April 2, says the Finnish Meteorological Institute (FMI). It defines thermal spring as when the mean daily temperature rises permanently above 0° C. Other parts of southern Finland are expected to follow suit within the next few days.
“Thermal spring is usually the shortest of Finland’s seasons, typically lasting six to eight weeks,” says Yle meteorologist Toni Hellinen.
He points out that thermal spring does not necessarily mean days will be warm, though. Nights remain quite cold and the mean temperature may be just barely above freezing.
First night above zero?
“However the subzero nights will end soon,” Hellinen adds.
“Temperatures may remain above zero in some parts on Thursday night, or over this weekend at the latest.”
Spring proper should begin soon although the forecasts call for chilly, cloudy and rainy weather, he says. The rain is good news.
"Rain speeds up the melting of snow and also improves the air quality, particularly in cities such as Helsinki where street dust has again been a problem,” he notes.
Here comes the flood
The protracted cold weather has also delayed spring flooding by nearly a month.
The Uusimaa region, which includes the Helsinki area, should see the first signs of flooding this weekend.
“At the moment there is significantly more snow on the ground than normally, 110-130 millimetres, which is locally nearly twice as much as usual. This of course indicates that there will be larger than usual spring floods,” says Kari Rantakokko, the senior environmental official at the Uusimaa Centre for Economic Development, Transport and the Environment.
He expects flood peaks to occur in late April. The more quickly temperatures rise, the higher flood levels will be. The Uusimaa Centre has already begun stepped-up monitoring of rivers around the region.
“There’s solid ice with a thickness of about 60 centimetres on most of these rivers,” Rantakokko says. “Of course we’re a bit worried about this ice forming dams, but we hope that the thawing will take place slowly enough that they don’t form.”
Still driving to Hailuoto
Meanwhile near Oulu, the ice road across to Hailuoto Island is still open, the latest in the spring since 1997. Road officials opened the 10-kilometre route on January 5 this year. The speed limit on the ice road is 50 kilometres an hour, and there is a weight limit of two metric tons. Hailuoto has a year-round population of just under 1,000.