The Finnish Meteorological Institute (FMI) has issued an array of warnings across southern parts of the country for Saturday.
The agency has posted a heavy rain warning for areas from the Turku area in the southwest to North Karelia in eastern Finland. The FMI says that heavy downpours of more than 20 mm an hour can be expected, beginning before noon and potentially continuing until around 11pm.
According to Yle's meteorologists, the heaviest rain will be along the area stretching from Hanko via Lahti up to Joensuu.
Flooding is likely in low-lying areas and flood-prone underpasses, and there is a risk of tyre hydroplaning, also known as aquaplaning, on waterlogged road surfaces.
Blackouts possible in southeast
There is a high wind warning for Kymenlaakso and South Karelia in the southeast beginning on Saturday afternoon. Strong westerly and northwesterly winds may be accompanied by strong gusts of 15 metres per second, likely toppling trees and causing power outages.
By Sunday, the heaviest rain will have moved off toward Russia, but thunderstorms are set to continue in parts of western and northern Finland. Eastern areas should be dry.
Temperatures remain cool throughout the country all weekend. Highs will be between 12 and 21 degrees Celsius, but staying in the single digits in parts of Finnish Lapland. Night-time temperatures range from four degrees up north to 11 in the south.
Small craft advisory at sea
There is a warning of gale-force winds and rough waves on southern sea districts, especially on the Gulf of Finland. There is a small craft advisory for eastern Baltic, which will likely see westerly to southwesterly gale force winds of 19 metres per second on Saturday evening.
Rough waves are predicted from the afternoon on, with significant wave height of more than 2.5 metres. The FMI says conditions may be dangerous for recreational crafts and small boats.
Strong northwesterly breezes of 13 m/s are also forecast for southern parts of Lake Saimaa in eastern Finland on Saturday evening.
The new week will start with similar unstable conditions as so far in July, with scattered showers and thunderstorms.