Bulgaria — Water Temperature in Seas, Lakes and Rivers

Sea Water Temperature Along the Coast

Places with the Warmest Sea Water Today

The Most Popular Seaside Places

Coastal Seas and Oceans

Water Temperature in Lakes and Rivers

Popular Lakes

Popular Rivers

Popular Places

Water Temperature and Swimming Overview

Water Temperature Trends

Bulgaria’s main bathing waters are along the Black Sea coast, where surface temperatures vary markedly with the seasons. In spring (March–May) coastal waters typically range from about 11–18 °C (52–64 °F), warming to comfortable summer values of roughly 20–27 °C (68–81 °F) in June–August; July and August often produce the warmest readings, particularly in shallow bays. Autumn (September–November) sees a gradual cooling, with sea temperatures commonly between 15–22 °C (59–72 °F), while winter months can drop to around 6–10 °C (43–50 °F). These seasonal patterns make June–September the primary period for recreational swimming on organized beaches, when conditions, lifeguard presence and water quality monitoring are at their best.

Swimming Conditions

Inland water bodies show greater variety: lowland lakes and the Danube can reach summer temperatures similar to the coast, about 20–26 °C (68–79 °F), while shallow coastal and salt lakes may warm even more on hot days. Mountain rivers and alpine lakes remain cool year-round, commonly in the 4–12 °C (39–54 °F) range and only marginally warmer in summer, so they are less suited to prolonged swimming. Swimming is generally allowed in designated beaches and many lakes, subject to local rules, water-quality advisories and safety measures; river swimming is possible but calls for extra caution because of currents, variable depths and colder temperatures. A small minority practice winter or ice swimming, but for most visitors the warm summer months offer the safest and most comfortable opportunities for bathing in Bulgaria.