Water temperature of the Baltic Sea in september Where to swim in the Baltic Sea in september 2025?

Several countries border the seaside of the Baltic Sea, including: Germany, Denmark, Estonia, Finland, Lapland, Latvia, Lithuania, Poland, Russia and Sweden. We measure the water temperature daily in these countries and archive it in order to calculate monthly averages, like those of the month of september.

The seasonal average for the water temperature in the month of september is between 50°F and 64°F. The lowest sea temperature measured this month is 31°F and the highest is 70°F.

The sea temperature map of the Baltic Sea in september

The map below presents a monthly average of the water temperature of the Baltic Sea for the month of september for several coastal cities. You can zoom and move around on the map. By clicking on the markers, you can see sea temperature details by city in september.