Friday is expected to be largely dry and sunny across Finland, with only local showers possible in northern Lapland.
Temperatures in much of southern and central Finland will hover around the 25-degree-Celsius threshold that marks a "hot day" by Finnish standards, while cooler conditions will prevail in the north.
The weather is set to take a turn over the weekend, according to Yle meteorologist Henriikka Heikinoja.
"The weekend is shaping up to be exceptionally wet," Heikinoja said. "It's not the time to be planning outdoor chores."
Saturday will bring the first bands of rain to southern and central Finland, accompanied by the risk of scattered thunderstorms. Eastern Finland and parts of Lapland are likely to remain comparatively dry.
Temperatures will also begin to fall, with most regions dropping below 20 degrees Celsius, although southeastern Finland could still see locally hot conditions.
By Sunday, a low-pressure system is forecast to move directly over the country, bringing widespread and, in places, heavy rainfall.
Central areas are expected to bear the brunt of the downpours, with some areas receiving more than 50mm of rain within 24 hours.
"The weather will cool, continuing into the early part of next week," she added.
Strong, gusty winds will add to the unsettled conditions both on land and at sea. The Finnish Meteorological Institute (FMI) has issued warnings for high winds and rough seas in the northern and southern parts of the Bothnian Sea on Sunday.
