Highest Water Temperature of the Baltic Sea: ~25°C (77°F) in Summer

Peak Warmth

The Baltic Sea reaches its highest temperatures in July and August, typically around 25°C (77°F) in shallow coastal areas and sheltered bays (e.g., Gulf of Finland, Gulf of Riga, Curonian Lagoon).

Average & Range

• Annual average: ~8.5°C (47°F)
• Winter: Near freezing (0–2°C); much of north freezes over
• Summer surface: 15–25°C depending on location, depth, weather

Why So Variable?

• Shallow (avg 55 m) → warms/cools fast
• Low salinity (brackish) → freezes easier, stratifies
• Limited exchange with North Sea (Danish straits)
• High latitude (53°–66° N) → extreme seasonal sun angle

Swimming?

Popular in southern/central coasts (Poland, Germany, Denmark, southern Sweden, Finland) in July/Aug. Northern Gulf of Bothnia stays cold.