On Saturday, the Western Finland Coast Guard warned boaters on the western sea areas of powerful thunderstorms.
The Coast Guard issued a small craft advisory, urging those boating in the Kvarken and Åland archipelago areas to stay in port until a band of thunderstorm has passed. The Kvarken is a narrow part of the Gulf of Bothnia between Finland and Sweden, separating the Bothnian Bay from the Bothnian Sea, the northern reaches of the Baltic.
The Finnish Meteorological Institute said on Saturday afternoon that a belt of severe thunderstorms was moving northward along the coast.
"There will likely be thunderstorms in western sea areas throughout the next 24-hour period," meteorologist Jani Parviainen told the Finnish news agency STT on Saturday afternoon.
"Thunderstorms may occur during this evening in the Bothnian Sea and the Kvarken. In addition, the new storms rising from the direction of the Baltics are likely to survive all the way to the northern parts of the Bothnian Sea and may intensify in some places on Sunday morning," he said.
According to Parviainen, boaters on the northern Baltic Sea should beware of sudden gusts of wind through the rest of the weekend.
"Thunderstorms can always be accompanied by strong gusts, which may reach 15 metres per second," he said.
Warnings of winds, rain, heat, UV radiation and forest fires
According to Yle meteorologists, thunderstorms are expected to move into Northern Ostrobothnia and Finnish Lapland on Sunday, with only a few showers in the south.
On Monday, showers and thunderstorms will become less frequent and dry conditions will return to much of the country.
Besides strong winds on western sea districts, there are warnings of heavy rain and thunderstorms in western Finland and oppressive heat throughout the country except Finnish Lapland. Ultraviolet radiation is intense in many southern and central parts of the country. There is also a high risk of forest fires throughout the country.