September was exceptionally warm and at the end of September the Baltic Sea water much warmer than usually. Nevertheless, because of several storms in October that mixed the water up, it could cool down as the weather got colder. The first ice was observed in Tornio on 22 October and in the last week of October more new ice was formed off the coast in the Bay of Bothnia. At the beginning of November there was also thin new ice in the Vaasa archipelago.

November was cold. More ice was formed continuously in the Bay of Bothnia, and the northeasterly wind pushed the ice formed outwards to the sea. The first assistance restrictions came to force in Tornio, Kemi and Oulu on 22 November 2023. At the same time, the stormy southeasterly wind piled the ice off the coasts in Kemi and Tornio. After that the weather became even colder and new ice formed in the inner bays of the Bothnia Sea, the Archipelago Sea and the Gulf of Finland. Icebreaker Kontio started the icebreaking season by leaving Helsinki on 23 November. At the time, the thickest fast ice of the coasts was 30 cm and there was thin drift ice to the Kemi 1 lighthouse and to the southwest of Merikallat. As the month changed, the water temperatures were about one and a half degrees colder than the average in the Bay of Bothnia and in the Bothnian Sea. In the Gulf of Finland the water temperatures were average.

The beginning of December was cold, and the amount of ice increased. In the middle of the month the ice-covered area was over 50,000 km². Icebreaker Voima started icebreaking season in Vaasa. During the week 51 the weather was milder with strong westerly winds and the amount of ice didn´t increase. The ice field in the Bay of Bothnia was slightly ridged, but a large part of the drift ice field off the fast ice remained fairly level. As Christmas began, the weather cooled down again.

Despite a short temperate period, January was cold until the 20th and its first week was even unusually cold. It was -20°C in the south and -40 °C in the north. The Bay of Bothnia was totally covered with ice on 3 January 2024, about a month earlier than the average, and new ice formed in all sea areas. In the Archipelago Sea, the outer archipelago had level ice on 7 January and the ice-covered area grew to 108,000 km², which is clearly higher than the average at the time. There were six Finnish icebreakers operating. On January 21, the ice-covered area was 119,000 km². At the end of the month, the weather was mild, and no new ice was formed. The strong southwesterly winds of the last days of January and early February piled the ice field in the Bay of Bothnia and the ice-covered area decreased to 52,000 km².

After February 5, cold air came to Finland from northeast and new ice was formed again. The Bay of Bothnia was totally covered with ice again, and there was not much open water in the Bothnian Sea as well. In the Gulf of Finland there was drift ice to Gogland and farther west thin level ice and new ice to the line Tallinn–Kantvik. The ice area was largest on 12 February, when it was 135,000 km². All Finnish icebreakers were assisting the traffic. Kontio, Otso, Sisu, Urho and Polaris were in the Bay of Bothnia, Zeus and Calypso in the Bothnian Sea, and Fennica, Nordica and Voima in the Gulf of Finland. Nevertheless, the cold period lasted no more than a week and a half.

The end of February was unusually mild. In the Bay of Bothnia the southerly wind pushed the ice almost completely to the north of the line Kalajoki–Skellefteå. In the Quark there was clearly more thick drift ice on the Swedish side. In the Gulf of Finland the drift ice field got compressed against the fast ice off the coast. The ice-covered area shrank to 58,000 km². In March the winds drifted the ice, but there were no major changes in the ice conditions. The ice-covered area grew slightly due to the cold period in mid-March.

In early April, the fast ice rotted in the western part of the Gulf of Finland and in the Archipelago Sea and these areas were ice-free on 17 April. At that time, the ice was rotten also in the Vaasa archipelago and the eastern part of the Gulf of Finland. In the Bay of Bothnia, the thickest ice of the drift ice field were in the early April on the Swedish side and along the coast of Finland there was an open water area, where new ice was formed from time to time. The end of April was also cold, and some of the Finnish Meteorological Institute´s weather stations measured cold records of April.

The drift ice remained on the west side of the Bay of Bothnia central line all May and a large open water area from the Quark to Kemi 1 lighthouse was preserved. The fast ice off the coast in Oulu rotted in the first week of May and the next week the fast ice field had become rotten in other sea areas too. On the mainland, there was as much as 16 hot days when the maximum air temperature exceeded 25 degrees in May. The ice melted from the Bay of Bothnia on May 20th. There were 80 cm thick ice floes among the drift ice field around Kemi 1. The last assistance restrictions were cancelled from Kemi and Tornio on 30 May. Icebreaker Otso returned to Helsinki on 31 May. At the time, there were still some rotten drift ice left on the west and south-west side of Kemi 2. The Baltic Sea was ice-free on June 4th.

The four-month period from October to January was clearly colder than the average in Fennoscandia. The first ice formed early, and the ice formation was fast in the beginning of the winter. The early January had freezing temperatures, which made the ice thicken well and the ice cover increase fast. However, in the end, because of the mild period at the end of February, the ice season didn´t become more severe. The ice season was average in terms of the extent of the ice. Compared to recent winters, the biggest differences to the past winter were the large ice cover in the Bothnian Sea and the freezing of the outer archipelago of the Archipelago Sea at a very early stage. Also the Bay of Bothnia froze over at an early stage. Nevertheless, the Bothnian Sea did not freeze completely. During the two mild periods in the winter the ice field in the Bay of Bothnia became ridged and was challenging for the traffic in some places. In the spring, freight traffic was at a standstill in Finnish ports due to a strike, which temporarily reduced the need for icebreaking assistance.

In the Bay of Bothnia the ice season started two weeks earlier than usual and ended more than a week later than usual. In the Quark the ice season started two to three weeks earlier than usual and ended more than two weeks later than usual. In the Bothnian Sea the ice season started two to four weeks earlier than usual and ended two weeks later than usual. The northern Baltic Sea stayed ice free the whole winter.

In the western Gulf of Finland ice season started just over two weeks earlier than usual and ended a week and a half earlier than usual. There were clearly fewer ice days than the average. In the central Gulf of Finland, the ice season started over three weeks earlier than usual and ended about a week earlier than usual. There were clearly more ice days than the average. In the eastern Gulf of Finland, the ice season started a week to more than three weeks earlier than usual and ended one week earlier than usual. There were some more ice days than the average.

In the Bay of Bothnia, in the Quark and the in the northern Bothnian Sea, there were more ice days than the average, while in the southern Bothnian Sea and the Gulf of Finland there were clearly fewer ice days than the average. The maximum thickness of fast ice varied between 40–80 cm in the Bay of Bothnia, 20–55 cm in the Bothnian Sea, 10–50 cm in the Archipelago Sea and 30–60 cm in the Gulf of Finland. In the open sea areas, the maximum ice thickness was between 30–80 cm in the Bothnian Bay, 5–25 cm in the Bothnian Sea, and 10–35 cm in the Gulf of Finland.

On 12 February 2024 the distance vessels had to navigate through ice to the ice edge was 284 nautical miles from Kemi and 186 nautical miles from St. Petersburg. Correspondingly the navigation distance in over 15 cm thick ice was 187 nautical miles and 120 nautical miles.