Finland's heatwave is likely to be disrupted on Sunday, when storm Riikka rolls into the country bringing dangerous conditions to eastern Finland, Kainuu, north-east Finland and Central Finland.
A cold front moves across the country from the east, bringing moisture and thunder as well as heavy rain to parts of the country.
Thunder and winds gusting at 25m/s are expected to hit the eastern half of Finland outside the northernmost parts of the country.
The Meteorological Institute's warning map offers more detail, with the orange shaded areas indicating a risk of storm damage. The warning text for South Savo reads 'Wind damage in numerous areas, including areas of uniform damage. Locally a need for significant debris clearance, long-lasting electricity outages and disruptions in telecommunication networks.'
The storm is expected to hit coastal Ostrobothnia overnight, reaching eastern Finland by the afternoon and creating more powerful thunder and lightning.
Meteorologists say that the weather could turn quickly on Sunday, with pleasant conditions becoming dangerous quickly.
"Heat, wind and moisture," said Yle meteorologist Anne Borgström. "When they are right, this kind of thunderstorm front is created. Dry air is flowing from the north-west, and ahead of it there is warm and humid air. That is broken up via thunder."
Temperatures to the east of the storm front could be 26-28 degrees Celsius, while those behind it are likely to be around 20 degrees.
Heavy rain is expected in Lapland.
If a storm in Finland is expected to cause significant damage, it is named according to the name day calendar in the University of Helsinki almanac. So far this summer that has meant storms named Ahti (21 June), Paula (22.6), and Aatu (23.6).