Weather at the sea – temps, precipitation, wind, and conditions over

When planning a seaside trip, it is worth knowing what weather to expect. Conditions on the coast differ from those inland—the sea warms and cools more slowly, so it reduces summer heat and releases stored warmth in autumn and winter. Wind also plays an important role, affecting perceived temperature and beach conditions. Below, we explain how temperature, precipitation, wind, sunshine and Baltic Sea water temperature change throughout the year.

• The warmest months by the sea are July and August, when the average day-and-night temperature is about 18°C.
• April usually has the least precipitation.
• Summer has most sunshine: about 8–9 hours daily on average.
• Baltic Sea water is warmest in July and August—usually around 18–21°C.
• Wind can significantly reduce the perceived temperature, so beach conditions may differ from thermometer readings.
• Coastal temperatures show an upward trend from year to year, although precipitation still varies greatly between years.
• The seaside is worth visiting year-round—just match your activities to the season and current weather.

Weather on the Polish coast by month

The basis for determining typical weather conditions on the Polish coast is the IMGW-PIB climate normals, based on 30 years of measurements from 1991 to 2020. Measurements were taken at synoptic stations, including Kołobrzeg, Ustka, Łeba and Hel. For each month, IMGW compiles the average air temperature, average minimum and maximum temperatures, precipitation totals and frequency, sunshine duration and cloud cover. The normals were calculated according to the guidelines of the World Meteorological Organization (WMO).

Own compilation based on IMGW-PIB 1991–2020 climate normals for stations in the coastal towns of Świnoujście, Kołobrzeg, Ustka, Łeba, Hel and Gdańsk. Averages were calculated from available values for the listed stations. For average temperature, 5 stations were used—IMGW does not provide a complete normal for Gdańsk. For sunshine duration, 3 stations were used: Kołobrzeg, Łeba and Hel—complete normals are unavailable for Świnoujście, Ustka and Gdańsk.

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Air temperature by the sea

The table’s average temperature is the monthly average of daytime and nighttime temperatures. For guests planning a stay, maximum temperature is more useful because it better reflects the warmest part of the day. Under IMGW normals (1991–2020), it is about 2.5–3.8°C in winter at the coastal stations analysed. In spring, it rises from about 6°C in March to 16°C in May; June averages about 20°C, and July and August about 22°C. In autumn, it drops from about 18°C in September to 7°C in November.

The 1991–2020 normals enable comparison with later years. IMGW compares, among other things, average annual air temperature on the coastal belt, meaning the region encompassing Poland’s Baltic coast. In 2021, it was 9.0°C, 0.1°C above normal. In 2023, it reached 9.8°C, 0.8°C above normal; in 2024, 10.7°C—1.8°C above the 1991–2020 normal. These data match the long-term trend of rising coastal temperatures.

Air temperature alone does not fully reflect conditions experienced on the beach. That is why perceived temperature is much more important by the sea. For example, at 18°C, strong wind can cause the body to lose heat much faster, making conditions feel considerably colder than the thermometer indicates. Conversely, with light wind and full sunshine, the same 18°C will feel much warmer.

Day–night temperature difference

Sea temperatures can change noticeably during the day. According to IMGW normals for the coastal stations analysed, in winter, average maximum temperature is usually about 4–5°C above average minimum; in spring, the difference reaches about 6–8°C; in summer, about 8°C; and in autumn, declines from about 7°C in September to about 4°C in November. Thus, daytime/nighttime differences are greatest from late spring to summer’s end.

When is it warmest by the sea?

July and August are the warmest months on the Polish coast. According to IMGW normals for 1991–2020, the average monthly temperature at the coastal stations analysed is about 18°C then, while the average daytime maximum is about 22°C.

When is it coldest by the sea?

January is the coldest month on the Polish coast. According to IMGW normals for 1991–2020, the average monthly temperature at the coastal stations analysed is about 0.6°C then, while the average daytime maximum is about 2.5°C. Values begin to rise slightly in February—the monthly average is about 1°C and the average maximum about 3.3°C.

Rainfall by the sea

In addition to monthly rainfall totals, IMGW also reports the number of days when daily rainfall reached at least 0.1, 1, 5, 10, 20, 30 or 50 mm. At the lowest threshold, ≥0.1 mm, the coastal stations analysed average about 11–19 such days per month. However, this threshold includes even very light rainfall.

In practice, rainfall that may significantly disrupt beach time, walks and other outdoor activities can be defined as a daily total of at least 10 mm, or 10 litres of water per square metre. Such days are not frequent. Studies of the Polish coast recorded an average of about 13–19 days with rainfall ≥10 mm throughout the year. Importantly, they occur most often in warmer months, when they can bring pleasant cooling. A daily total does not mean it rains all day—10 mm may fall during a short downpour or over several hours.

When does it rain most by the sea?

The highest monthly rainfall totals on the Polish coast occur in July and August. According to IMGW normals for 1991–2020, the average for the coastal stations analysed is about 76 mm in each month. Days when daily rainfall exceeds 10 mm occur only about twice a month. In subsequent months, totals gradually fall—to about 67 mm in September and 63 mm in October. Higher summer rainfall totals are therefore mainly due to more frequent storms and short downpours, during which a large part of the monthly normal may fall within a few hours.

When does it rain least by the sea?

April has the lowest monthly rainfall total on Poland’s coast. IMGW normals (1991–2020) give about 30 mm for the analysed coastal stations. Totals are slightly higher in February (about 33 mm) and March (about 36 mm).

Wind by the sea

Wind is one of the most characteristic features of weather on the Polish coast. The open sea and limited terrain obstacles that could weaken airflow contribute to higher wind speeds here. According to IMGW data for 2009–2018, the average annual wind speed at the coastal stations analysed was about 4.3 m/s. The lowest value was recorded in Świnoujście—3.3 m/s—and the highest in Ustka—5.2 m/s. In practice, this usually means gentle gusts clearly felt on the face, moving leaves and creating small waves at sea.

Benefits of wind by the sea

Besides providing pleasant cooling in warmer months, the sea wind has other benefits. It creates waves which, as they break on the shore, release sea spray—tiny water and salt particles containing small amounts of iodine. The most spray is produced when the sea is rough, so its concentration on the shore rises during windy weather.

See also: When is iodine most abundant by the sea?

Wind and storms also matter to people looking for amber. Strong waves disturb sediments and material on the seabed, then wash amber ashore with seaweed and other light debris. The best chance of finding amber is therefore after strong winds and storms.

Sunshine by the sea

IMGW defines sunshine duration as the time when direct solar radiation reaches the surface. After converting the 1991–2020 normals for Kołobrzeg, Łeba and Hel, winter averages about 1–2.5 hours of sunshine per day; in spring, this rises from about 4 hours in March to almost 9 hours in May, and from June to August it is about 8–9 hours per day. In September, it falls to about 6 hours, in October to 3.5 hours, and in November to about 1.5 hours per day.

It is important to note that sunshine duration does not mean the length of the day, or the time from sunrise to sunset. For example, in June, the day on the Baltic coast lasts over 17 hours, but average sunshine duration is about 9 hours. The rest of the day may occur in the morning and evening, when the sun is low above the horizon.

Cloud cover over the Baltic

IMGW defines a cloudy day as one when average cloud cover exceeds 80% of the sky. According to the 1991–2020 normals, at the coastal stations analysed, the fewest such days occur in summer—about 4–5 on average in June and July and 3–4 in August. There are far more in winter—about 12 in February and 16 in January and December.

Baltic Sea water temperature

The best chance of warm Baltic water comes in the second half of summer. In August, sea-surface temperature can reach about 20°C. By comparison, in winter the Baltic temperature falls to just a few degrees.

It is worth mentioning the specific phenomenon of upwelling. Wind pushes warm surface water away from the shore, allowing much cooler water from deeper Baltic layers to rise. That is why, during hot weather, nearshore water may be only a dozen degrees despite being much warmer a few days earlier. When planning a swim, check the current water temperature at the specific bathing site.

Why does seaside weather change so quickly?

The Baltic itself also affects changing weather on the coast. Passing fronts and low-pressure systems can quickly change wind direction and speed, temperature and cloud cover. Over open water, winds may also be significantly stronger—in active weather systems, IMGW forecasts coastal gusts up to several dozen kilometres per hour stronger than inland.

In summer, the sea breeze is also important. On sunny days, land heats faster than the sea, so cooler air from the Baltic flows towards the beach. This can lower the temperature by the sea and change wind direction. IMGW forecasts sometimes show temperatures above 30°C inland but several degrees lower around the Gulf of Gdańsk when the sea breeze arrives.

Is long-range seaside weather reliable?

The later the forecast period, the less accurate it is. Forecasts for several weeks or months mainly show general trends, such as whether it will be warmer, cooler, drier or wetter than usual. Check the exact forecast for your chosen day only a few days before travelling.

Seaside weather all year round

Baltic conditions change mainly with the seasons. Summer brings the highest air and water temperatures and the most sunshine; spring has less rainfall, while stronger winds and more cloud are more common in autumn and winter. Rainfall varies considerably by year, so it shows no clear trend like temperature. IMGW data show a clear long-term warming trend: in 2024, the annual average in the Coastal Regions was already 1.8°C above the 1991–2020 norm.

You can visit the seaside all year round—the main change is how you spend your time. Summer is ideal for beaches and swimming; spring and early autumn for walks, trips and outdoor activities. Cooler, windier months are perfect for long seaside walks, amber hunting or relaxing at a SPA.

Sources:

• https://klimat.imgw.pl/pl/climate-normals/
• https://baltyk.imgw.pl/ftp/ocena/OCENA_STANU_2019_NA_TLE_2009-2018.pdf
• https://rdsm.gios.gov.pl/images/Pliki/Oceny%20roczne/OCENA%20STANU%202024%20NA%20TLE%202014-2023.pdf