May and June are the best months to visit — warm but not hot (18–23°C), relatively dry, and the city is at its liveliest with outdoor events. The Keistad Jazz Festival in May fills the medieval centre with live music on every square.
Summer (July–August) is warmer and busier. Autumn is quiet but atmospheric, especially along the canals. Winters are mild by Dutch standards (2–6°C) but the Atlantic influence means it can turn cold and breezy without warning — pack layers. If you hit a cold snap with frost on the canals, you will see Amersfoort at its most picturesque.