Wave measurements in the sea areas around the Finnish coast have been made since the 1970’s, first by the Finnish Institute of Marine Research and now by the Finnish Meteorological Institute. Even if the Baltic Sea is small compared with the oceans, it is able to generate waves of respectable heights. The highest waves in the Baltic Sea are common during storms in the big oceans, but higher waves rare even there.
The biggest basin of the Baltic Sea, the Baltic Proper, has the most severe wave climate in the Baltic Sea. During a storm on 22 December 2004, the significant wave height in northern Baltic Proper reached 8.2 metres and the highest individual wave height was 14 metres. The former record at the measuring station was 7.4 metres, which was measured twice in December 1999. Significant wave heights over 7 metres have been measured in January 1984 at Almagrundet near the Swedish coast and in October 2009 in the southern Baltic Proper (SMHI).
The highest measured significant wave height off Helsinki in the Gulf of Finland is 5.2 metres. It was measured on 15.11.2001 and the highest individual wave reached 9 metres. At this location, both easterly and westerly winds are able to generate waves this high, but much higher they are not expected to grow due to the narrow shape of the Gulf of Finland.
In the southern Bothnian Sea, a significant wave height of 5.5 metres, measured in 1970s, is still holding the record. The highest individual wave was 10 metres.
The highest measured significant wave height in the Bay of Bothnia is 3.1 metres with a highest individual wave of 5.6 metres.
The longest timeseries of the measurements are from the Northern Baltic Proper and from the Gulf of Finland. In the other areas the measurements have been made during shorter periods. The wave measurements are also local: higher significant wave heights than mentioned above are possible in the Baltic Sea.
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