Copenhagen sits on the coast of Zealand and has a maritime climate with mild but grey winters and pleasant summers. The best time to visit is May through September, when daylight lasts well into the evening, outdoor cafes are open, and the parks are full of life. June through August brings the warmest weather (around 20-22C) and the longest days, but also the biggest crowds and highest prices.
Spring and autumn are the sweet spot for budget travellers. April and October bring fewer tourists, lower hotel rates, and enough daylight to explore comfortably. The city's many music festivals cluster in the warmer months, with the Copenhagen Jazz Festival in early July being the highlight.
Winter is cold, dark, and wet, with only a few hours of daylight in December and January. But the city compensates with candlelit bars, Christmas markets, and the warm glow of hygge. Hotel prices drop significantly, and museums are blissfully uncrowded.