The Gulf of Finland's 20-year high-temperature record was broken on Wednesday when the seawater was recorded as being over 25 degrees (c).
The Finnish Meteorological Institute said the water temperature buoy, located in the middle of the Gulf of Finland, gave a daily average of 25.2 degrees. The highest figure recorded on the same day was 26.6 degrees.
The Gulf of Finland's daily average water temperature is normally around 17-18 degrees at this time of year. The institute's heat records go back 20 years.
Editor: Helen Wright