Karlskrona's winters are cold and unpredictable, with temperatures often dropping below freezing in January and February, but occasionally rising into the mid-single digits. Spring arrives slowly, with March temperatures gradually warming up towards double digits, while April and May see a steady increase to average highs around 15-20°C. Summer is mild, with June and July being the warmest months, averaging highs above 25°C, although August can be slightly cooler. Autumn brings a return to more moderate temperatures in September and October, before cooling down again towards winter levels by November and December.