The climate of Rønne is Baltic, that is to say, relatively continental, with cold winters and mild to pleasantly warm summers.
The city is located on the island of Bornholm, which lies to the east of the main islands of Denmark, and to the south-east of Sweden, and has a relatively dry and sunny microclimate.
The average temperature of the coldest month (February) is of 0.9 °C (34 °F), that of the warmest month (July) is of 18.2 °C (65 °F). During the coldest winters, the temperature dropped to -15 °C (-4 °F) in March 1987 and January 2003. In summer, the temperature reached 30 °C (86 °F) in August 2018 and July 2019. Here are the average temperatures.
Rønne - Average temperatures
Min (°C)-1-103711141411741
Max (°C)4361115192221181395
Min (°F)303032374552575752453934
Max (°F)393743525966727064554841

Precipitation amounts to 485 millimeters (19.1 inches) per year: it is therefore quite scarce. It ranges from 25 mm (1 in) in the driest month (February) to 55 mm (2.2 in) in the wettest (September). Here is the average precipitation.
Rønne - Average precipitation

On average, there are around 1,800 sunshine hours per year. In summer, also due to the length of the days, the sunshine amount is quite good. Here are the average sunshine hours per day.
Rønne - Sunshine

The sea temperature ranges between 3 °C (37 °F) and 18 °C (64 °F). So, it never becomes warm for swimming (if not for Northern Europeans). Here are the average sea temperatures.
Rønne - Sea temperature
Temp (°C)43359141718161285
Temp (°F)393737414857636461544641


Best Time

The best time to visit Rønne is the summer, from June to August, since it is the mildest season. However, you must take into account some rainy days and a bit of cold at night.