June through August is when Gothenburg comes alive. The days are long -- up to 17 hours of daylight in midsummer -- and the city's cafes and bars move outdoors. Temperatures sit in the mid-teens to low twenties Celsius, which counts as warm by Swedish standards. This is also when the archipelago is at its best for swimming and island hopping.
Spring (April to May) is pleasant and less crowded. Winter (November to March) is dark and cold, with only about seven hours of daylight, though the Christmas markets at Liseberg are worth a visit.
Festivals
The Hammarkullekarnevalen in late May or early June is a colourful three-day carnival with a street procession, salsa dancing, and Caribbean music. The Gothenburg Music Festival at the end of June brings bands and orchestras marching along the Avenyn. Throughout August, the Gothenburg Dance and Theatre Festival takes over stages across the city. On 13 December, the Lucia Festival features a traditional choir procession led by a young girl wearing a crown of candles.