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The Black Sea season in Romania: when it opens, how long it lasts and when the water is warmest

The rusted hull of a cargo ship on a calm sea at dusk, seen from the empty beach, with two wooden boats pulled up on the sand
The rusted hull of a cargo ship on a calm sea at dusk, seen from the empty beach, with two wooden boats pulled up on the sand · Cristian Coaja · Unsplash License

By law, the season on the Romanian Black Sea coast opens on 1 May and closes on 30 September: that is what the ordinance on the use of the Black Sea beach says. On the sand, the real season is shorter. The sections with sunbeds are set up from mid-May, lifeguards are on duty only for as long as each town hall has contracted them, and the water only reaches swimming temperatures in June. It is warmest at the end of July and in August: at the Mamaia station of the INCDM "Grigore Antipa" (the National Institute for Marine Research and Development), the average measured between 11 and 22 August 2025 was 25 °C.

Below you will find, month by month, the water and air temperature, with the source and period of every figure, what is open on the coast, why the water can suddenly turn cold in high summer and where to go to the seaside in September. The resorts, from north to south, are in the guide to the Romanian coast, and the beach flags and lifeguard hours in the guide to jellyfish, sharks and flags.

In short

  • The tourist season on Romania's Black Sea coast begins on 1 May and ends on 30 September, under art. 3 of Emergency Ordinance (OUG) 19/2006.
  • Beach sections are generally set up from mid-May, and lifeguards are on duty only during the period contracted by each town hall: in 2026, 1 June – 14 September at Costinești and 1 May – 30 September at Năvodari.
  • The long-term average sea temperature in June on the Romanian coast is about 20 °C, according to the INCDM "Grigore Antipa".
  • The water is warmest at the end of July and in August: at Mamaia, the INCDM measured an average of 24.7 °C between 28 July and 8 August 2025 and 25.0 °C between 11 and 22 August 2025.
  • In high summer the water can cool by 5–7 °C within a few days, when the west wind pushes the warm water out to sea; in June 2026 it dropped from about 21 °C to 16 °C.
  • The average air temperature in Constanța is 23.0 °C in July and 22.9 °C in August, 20.7 °C in June and 18.7 °C in September (ANM, 1961–2021).

The seaside season month by month: water and air temperature and what is open

The table brings together the three things you look up before choosing the month. For the air there is an official 60-year average from the National Meteorological Administration (ANM). For the water, neither the ANM nor the INCDM publishes a table with the long-term average for each month: the INCDM gives only the average for June, a chart of the monthly averages and the readings from the Mamaia station in its summer bulletins. That is why the water column shows the measured values, with their periods, and no figure is published for May.

MonthSea waterAir in Constanța (monthly average)What is open on the coast
Mayno official average published16.1 °Cthe legal season starts on 1 May; beach sections are set up from mid-month; lifeguards at Năvodari from 1 May (2026)
June~20 °C long-term average; 21 → 16 °C within a few days, in mid-June 202620.7 °Clifeguards on the developed beaches (at Costinești from 1 June 2026); the train to Mangalia, reopened in June 2026; the Cold Baths (Băile Reci) at Techirghiol, open in June 2026
July21.4 °C (30 Jun – 14 Jul 2025), 20.7 °C (14–25 Jul 2025), 24.7 °C (28 Jul – 8 Aug 2025)23.0 °Chigh season: Aqua Magic on peak hours; lifeguards until 20:00 from mid-month; the Mangalia–Olimp electric buses from 13 July (2026)
August25.0 °C (11–22 Aug 2025), 22.6 °C (25 Aug – 5 Sep 2025)22.9 °Cpeak of the season; parking in Zone 0 of Constanța and Mamaia is charged round the clock until 31 August
September22.6 °C at the start of the month (25 Aug – 5 Sep 2025); the rest of the month not published18.7 °Clifeguards at Costinești until 14 September, at Năvodari until 30 September (2026); the Mamaia gondola lift and some of the bars close in mid-month
October13–14 °C, the normal for the end of the month, according to the INCDM13.4 °Cno lifeguards; the Constanța beach sections are packed away at the start of the month; the beach stays open
November – Aprilnot published1.0 °C in January, 10.4 °C in Aprilthe beach is open, but with no sections and no lifeguards; the towns and museums run all year

Water: INCDM "Grigore Antipa", Mamaia monitoring station (bathing water bulletins, July–September 2025); the June average and the June 2026 episode, INCDM quoted by ZIUA de Constanța (16 June 2026); October, INCDM quoted by Newsweek România (22 October 2023). Air: ANM, long-term monthly average 1961–2021, Constanța station. What is open: the attraction pages on the site, checked on 30 October 2026.

Rows of thatched parasols and wooden sunbeds on empty sand at sunrise, with the calm sea behindTop 100

Mamaia

Constanța, CTOpenFree
Seaside

Black Sea water temperature by month: what the INCDM measures

The water off the Romanian coast is measured by the "Grigore Antipa" National Institute for Marine Research and Development (INCDM) in Constanța. Its series from the Constanța station begins in 1959. In summer, the institute publishes bathing water bulletins every two weeks, with the surface water temperature measured at the permanent station at Mamaia.

The long-term average for June is, according to the INCDM, about 20 °C. For the other months the institute does not give the figure, only the deviations from it. The chart of monthly averages at Constanța in the INCDM study for the Ministry of the Environment (2018) shows the same cycle every year: the water is coldest in January–February, warms from April, peaks in July or August and falls from September. Between 2006 and 2017, the monthly peak was around 23–27 °C.

The same study finds no clear long-term trend from 1959 to 2017, but over the last 12 years of the series the water warmed by about 0.03 °C a year. Today's water temperature is not a subject for a guide: follow the INCDM bulletins or the ANM forecasts.

When the sea is warmest in Romania

At the end of July and in August. In summer 2025, the highest averages measured by the INCDM at Mamaia were 24.7 °C between 28 July and 8 August, with highs of 26.5 °C, and 25.0 °C between 11 and 22 August. In the last week of August and the first days of September the average fell to 22.6 °C, with values between 19.8 and 24.4 °C.

June is the month in which the water is only just warming up: its long-term average, about 20 °C, is roughly five degrees below the averages measured in August 2025. September starts with the water still above 20 °C, and the air cools faster than the sea: in Constanța its average is 18.7 °C, against 22.9 °C in August. If you want warm water and emptier beaches, the first half of September is the compromise.

Why the sea is cold in high summer

The phenomenon is called upwelling. When the wind blows for a few days from the west, off the land, it pushes the warm surface water out to sea, and cold water from the depths takes its place. This is how the INCDM explained the cooling in mid-June 2026, when the water dropped within a few days from about 21 °C to 16 °C.

It happens in July too. In 2025, the water at Mamaia reached 17 °C on 10 July and 14 °C on 24 July, up to 7 °C below the month's long-term average, because of the winds and currents. The episodes are temporary: once the wind changes, the water returns to seasonal values within a few days. A short holiday early in the summer can therefore catch cold water even in July.

When the seaside season opens: 1 May, by law

The date is set by Emergency Ordinance no. 19/2006 on the use of the Black Sea beach. Art. 3 says that the summer tourist season on the coast begins on 1 May and ends on 30 September, every year, so in 2026 and 2027 as well. Art. 4 requires town halls with tourist beaches to organise a lifeguard service and first-aid posts.

On the beach, the opening comes in stages. The sunbed sections at Mamaia and on the Constanța City Beaches are generally set up from mid-May. Lifeguards start on the date in each town hall's contract: in 2026, at Năvodari – Mamaia Nord Beach from 1 May, at Costinești from 1 June. Mangalia town hall signed a five-month contract in April 2026 for its beaches and those of the southern resorts. The hours for each beach are in the guide to lifeguards and flags.

The coast on 1 May: what you will find open

On 1 May the season is open on paper, but the beach is only getting started. The sections are set up from mid-month, so many stretches are still bare sand, and there are lifeguards only where the town hall's contract starts on 1 May, as it did at Năvodari in 2026. The average air temperature in Constanța is 16.1 °C in May, and no official average is published for the water; the INCDM puts only June at about 20 °C.

The 1 May weekend is therefore more for the promenade, the town and the terraces than for swimming. Constanța, with the Constanța Casino and the Constanța Peninsula, can be visited all year, and the Callatis Citadel in Mangalia is open too, in May on its off-season hours, Monday to Friday.

The coast in June

June is the month when everything starts: lifeguards are on duty on the big beaches, parking in Zone 0 of Constanța and Mamaia is charged round the clock from 1 June, and the Callatis Citadel switches to its summer hours, daily. In 2026, the Cold Baths (Băile Reci) at Lake Techirghiol opened in June, and the railway line to Mangalia, closed since October 2025, reopened in June as well.

The water averages about 20 °C, so it is fine for swimming, but it can drop suddenly during upwelling episodes. The average air temperature in Constanța is 20.7 °C. The wild Corbu Beach is still almost empty, and Tuzla Beach is quiet.

When the seaside season ends

Legally, on 30 September. In practice, the beaches wind down one by one, from the second half of August to the beginning of October:

  • 31 August: round-the-clock parking charges end in Zone 0 of Constanța and Mamaia, and so do the summer hours of the Callatis Citadel.
  • mid-September: the Mamaia gondola lift and some of the bars close, and at Năvodari the clubs and terraces; around the same time, depending on the weather, the Cold Baths at Techirghiol shut.
  • 14 September: the last day with lifeguards at Costinești, in 2026.
  • 30 September: the last day with lifeguards at Năvodari, in 2026.
  • early October: the sunbed sections on the Constanța beaches are packed away.

After that, the beach remains public property and access is free, but there are no lifeguards. You go into the water at your own risk.

Where to go to the seaside in September

Choose according to how late in the month you come. In the first half of September almost everything is open, the water is above 20 °C and the August crowds have gone. In the second half, what matters is where there are still lifeguards and developed sections.

  • Năvodari – Mamaia Nord Beach: in 2026 the lifeguards stayed on duty until 30 September, the latest on the coast among the published schedules.
  • Constanța City Beaches: the sunbed sections stay until early October, and the city has things to see in bad weather too.
  • Tuzla Beach and Corbu Beach: in September Tuzla is quiet and Corbu almost empty. There is no lifeguard at Corbu in any season.
  • Costinești: lifeguards until 14 September, in 2026; after that the resort empties quickly.

In September 2026, beach nourishment works began on Mangalia Beach and in Saturn, with stretches of building site until they are finished, expected before summer 2027. Which resort suits you otherwise is in the guide to choosing a resort.

The coast in October and in winter

From October the coast belongs to the towns. The water falls towards 13–14 °C at the end of the month, the normal given by the INCDM, and the average air temperature in Constanța is 13.4 °C in October and 1.0 °C in January. The Constanța Casino has had autumn–winter hours since 21 September 2026, Wednesday to Monday, and the Callatis Citadel is open Monday to Friday.

The treatments at Eforie Nord and the sanatoriums at Techirghiol and Mangalia run all year; the lake as a place for treatment is covered in the guide to salt baths. The beaches stay open, without lifeguards.

What to check before you go to the seaside

The details above change every year: lifeguard contracts and the parking and train schedules are announced in spring. Check on the page of the beach or the resort, and when you arrive ask at the lifeguard post until what time it is staffed. What each flag means and what to do about jellyfish is in the guide to jellyfish, sharks and flags. What to take to the seaside and how to get there are in the practical section of the guide to the coast.

Frequently asked questions

When does the beach season open in Romania in 2026?
On 1 May, as every year: OUG 19/2006 sets the tourist season on the coast between 1 May and 30 September. Beach sections are set up from mid-May, and in 2026 lifeguards started at Năvodari on 1 May and at Costinești on 1 June.
How long is the beach season on the Romanian Black Sea coast?
Five months, from 1 May to 30 September, by law. High season, with all the sections, the lifeguards and the summer transport, runs from June to mid-September.
When does the beach season end in Romania?
Legally, on 30 September. In 2026 the lifeguards left Costinești on 14 September and Năvodari on 30 September, and the Constanța beach sections are packed away at the start of October.
What is the Black Sea water temperature in June?
About 20 °C on average, according to the INCDM "Grigore Antipa". It can drop to 16 °C within a few days when the west wind brings up cold water from the depths, as in mid-June 2026.
When is the Black Sea warmest?
At the end of July and in August. At Mamaia, in 2025 the INCDM measured averages of 24.7 °C between 28 July and 8 August and 25.0 °C between 11 and 22 August.
What is the Black Sea water temperature in September?
At the start of the month, above 20 °C: between 25 August and 5 September 2025, the INCDM measured between 19.8 and 24.4 °C at Mamaia, with an average of 22.6 °C. No value is published for the second half of September.
Why is the Black Sea cold in July?
Because of upwelling: the wind from the land pushes the warm water out to sea and cold water from the depths replaces it. On 24 July 2025 the water at Mamaia fell to 14 °C; the episodes last a few days.
Is the Romanian coast worth it on 1 May?
For the promenade, the town and the museums, yes; for swimming, rarely. The average air temperature in Constanța is 16.1 °C in May, the beach sections are only set up from mid-month, and no official average is published for the water.
Where to go to the Romanian seaside in September?
To Năvodari – Mamaia Nord, where the lifeguards stayed until 30 September in 2026, or to Constanța, where the sections stay until early October. For peace and quiet, Tuzla and Corbu are the emptiest in September.

Sources

All guides