In the northern Bay of Bothnia the freezing started at the normal time in the beginning of November. The end of November and beginning of December were mild causing the ice cover to decrease. In mid December only the inner archipelago of the Tornio-Kemi area was covered in ice. Towards the end of December there was another short-lived cold spell causing ice to form off Oulu again.

The early January was mild with little freezing. Towards the end of January the weather turned colder and ice began to form in all sea areas, in the southern Bay of Bothnia and the Quark over one month later than usual and in the Sea of Bothnia, the Archipelago Sea and the Gulf of Finland approximately one month later than on average. In the end of January the open sea of the Bay of Bothnia was mostly open water, there was new ice in the Quark and the Gulf of Finland was covered in ice in the archipelago and in the east up to Motshjnyj.

The freezing continued in the beginning of February and the Bay of Bothnia was entirely covered in ice on 8 February, some three weeks later than average. Weather in February continued to be cold with ice forming in the Sea of Bothnia and the Gulf of Finland. The largest ice cover – 140 000 km² – was reached on the 23rd of February. The Bay of Bothnia and the Quark were covered in ice, the Sea of Bothnia was covered off the coast by an ice belt varying by width between 10 to 30 nautical miles, the Archipelago Sea was frozen and the ice edge in the Gulf of Finland ran along the line Utö–Mohni; the Gulf of Riga was also mostly frozen. Due to the occasional strong winds related to the mild winter areas of ridged ice were formed in the Bay of Bothnia over February, March and April. In the Gulf of Finland the ice was thinner with less ice ridging.

In March the ice conditions gradually declined and the ice became rotten in the Sea of Bothnia, the Archipelago Sea and the Gulf of Finland. These specified areas were free of ice in the beginning of April almost two weeks earlier than average. The Quark lost its ice cover towards the end of April approximately one week ahead of the average time and the Bay of Bothnia towards the end of May just about in normal schedule.

In the Bay of Bothnia the maximum thickness of fast ice was between 50 to 75 cm, in the Sea of Bothnia between 30 to 45 cm, in the Archipelago Sea between 10 to 30 cm and in the Gulf of Finland between 30 to 45 cm. Thickness of ice in the open sea area in the Bay of Bothnia varied between 20 to 50 cm, in the Sea of Bothnia between 5 to 30 cm and in the Gulf of Finland between 10 to 35 cm.

In the northern Bay of Bothnia the duration of the ice winter was average, in the southern Bay of Bothnia more than a month and in the Quark almost one and a half months shorter than average; in the Sea of Bothnia, the Archipelago Sea and the Gulf of Finland the ice winter was one and a half months shorter than average.

Simo Kalliosaari