Weather & Climate on Bornholm

Bornholm sits far out in the southern Baltic Sea, and that shapes its weather noticeably: the same temperate maritime climate found in Denmark and southern Sweden, but with summers that are often sunnier and drier, and winters that can bring more snow. The sea all around tempers both heat and frost and shifts the seasons. This guide brings together the climate figures that matter for trip planning – temperatures, sea temperature, rainfall, wind and the best time to visit by activity.

Current weather and forecast

This page doesn't show a live weather report. For today's weather and the coming days, use the official forecast from the Danish Meteorological Institute for Bornholm. Location-specific forecasts are also available for Rønne, Nexø and Sandvig.

The DMI site is in Danish, but its charts and weather symbols are easy enough to read. The weekdays are mandag (Monday), tirsdag (Tuesday), onsdag (Wednesday), torsdag (Thursday), fredag (Friday), lørdag (Saturday) and søndag (Sunday).

Temperatures through the year

Bornholm has a balanced, tempered temperature profile. The coldest month is February, with daytime highs around 3°C and lows around -1°C, while the warmest is August, at roughly 20°C by day and about 14°C at night. The genuinely warm season is short, lasting only around three months, from about mid-June to mid-September.

Real heat is the exception. The 30°C mark is only broken on isolated days at the height of summer, because the Baltic's cool water mass tempers the air temperature more than it does on the Danish mainland. For comparison, Denmark's all-time record of 36.4°C dates from 1975 in Holstebro in Jutland – a figure that's practically out of reach on a sea-surrounded island like this.

Over the longer term, warming against the reference climate is well documented. DMI's 1991–2020 climate normal puts Denmark's nationwide annual average at 8.7°C; 2024 came in at 9.8°C, around +1.1°C above that, making it the second-warmest year since records began in 1874, after 2014. 2023 to 2025 were three above-average warm years in a row. For trip planning, that doesn't mean expecting a scorching high summer, but it does mean leaning towards milder rather than cooler average years.

Sun, dry weather and the island's reputation

Bornholm is one of the driest and sunniest regions in Denmark – that's not tourist-board spin, it's borne out in the climate data. Annual rainfall runs to roughly 485 to 740 mm depending on location and source. Individual stations report figures around 705 to 714 mm in Sandvig and 693 to 731 mm in Svaneke; for Rønne, the numbers vary between about 485 and 742 mm depending on the dataset. The exact figure depends heavily on the measurement period used, but the overall picture is clear: comparatively little rain.

That fits with the long growing season. The growing period runs from around 19 April to 6 November – about 6.6 months, unusually long for this latitude. The island's mild climate is enough for figs to thrive in sheltered spots. Fig-growing is established enough here that a dedicated hardy variety exists, the Bornholm fig (Ficus carica 'Bornholm'), considered one of the most reliable fig cultivars for Nordic conditions.

To see this climatic advantage for yourself, head to Almindingen, the island's largest forest. It's home to the Arboretum, a 4 to 5-hectare forest botanical garden laid out in the 1930s by forester Valdemar Sejer. At this latitude – around 55°N – roughly 100 tree and shrub species grow here, North American ones in the northern part of the garden and Asian species in the south. Admission is free.

The Baltic Sea as a temperature regulator

The sea is the quiet lead actor in Bornholm's climate. It warms more slowly than the land in spring and only gives up its stored warmth reluctantly in autumn. As a result, spring and autumn set in noticeably later on the island than on the mainland, while late summer stays mild for longer – the sea's stored warmth pushes the season back.

In winter the same effect works in reverse: the relatively warm water keeps hard, sustained frost in check. That buffering effect is why Bornholm's extremes are blunted – less heat in summer, less harsh frost in winter, but a long, mild transitional season either side. For travellers, that's good news – even outside the main season, the weather stays fairly predictable and rarely extreme.

Sea temperature and the swimming season

Anyone planning to swim should watch the sea temperature, not just the air temperature. The Baltic's monthly average off Bornholm only passes 15°C towards the end of June and stays above it until around mid-September. It peaks in August at around 17 to 18°C; the 18°C mark is practically never exceeded as a monthly average.

For beach holidaymakers, that means a comfortable swimming window from late June to mid-September. On isolated days with stable high pressure, the shallow bays can warm up locally to 20 to 22°C – but that's the exception, not the average. The long, bright sandy beaches in the south are especially well suited for it; the beaches of Bornholm hub has an overview, including the expansive Dueodde beach.

Rain, wind and storm season

Rainfall is spread very unevenly across the year. Spring is the driest stretch: March and April, at only around 25 to 32 mm, are the least rainy months. Autumn is the wettest, running from September to November; October, at around 79 mm, is one of the rainiest months. The number of rain days also climbs towards autumn – averaging around 7.8 in September, 8.9 in October and 9.2 in November, making it the rainiest month overall.

A similar rule of thumb applies to wind: from mid-September to the end of March, Bornholm sees its windiest weather, with the main storm season falling in late autumn and winter. January, averaging around 30 km/h, is the windiest month, and May is by far the calmest. So if you're planning to cycle the wind-exposed coastal loop around the island, or go sailing, the calmer early summer is the better window.

Best time to visit by activity

Which month suits you best depends on what you're planning. Three clear profiles emerge:

• Swimming and the beach – late June to mid-September, once the sea passes 15°C. August is warmest, with July and August the most reliable swimming weeks.
• Beach, cycling and family holidays – June to September bring the most stable sunny weather and the longest days; June alone has more than 17 hours of daylight.
• Hiking and sightseeing – spring and autumn are ideal. At 8 to 17°C it's comfortable walking weather, the island is noticeably quieter, and the long bright days of early summer stretch out the day's programme.

In short: high summer belongs to the beach, while the shoulder seasons suit anyone after peace and mild temperatures rather than swimming water. For more on getting there and seasonal timing, see the guides to ferries and getting there.