Climate

In general Finland has an extreme swing between summer and winter, with bitterly cold winters when temperatures drop to -4ºF (-20ºC) in many areas, particularly in northern Lapland. Summer, by contrast, can be warm with temperatures rising to 68ºF (20ºC) or more. Temperatures as high as 86ºF (30ºC) are possible in the south and east of the country.
The capital, Helsinki, remains fairly temperate varying between an average of 63ºF (17ºC) in July to 23ºF (-5ºC) in February. In the far north the sun does not set for about 73 days during summer, while in winter the sun remains below the horizon for a 51-day stretch.

Current conditions

Helsinki-Vantaa Conditions and Forecast

Also, check here for a 5 day forecast.
Outside temperature variation at Otaniemi.