Debrecen has the climate of the Hungarian plain — hot summers, cold winters, and not much else in between. Late May through September is the most pleasant stretch, with long evenings on the terraces and the Nagyerdő at its best. The signature event is the Debreceni Virágkarnevál, the Flower Carnival, held on 20 August (St Stephen's Day): an enormous parade of floats covered in fresh flowers, drawing a quarter of a million spectators. Book accommodation months ahead.
Winter is cold (sometimes -15°C) but the thermal baths come into their own and the Christmas market on Kossuth tér is one of the better ones in eastern Hungary. Spring and autumn are quieter and pleasant for walking.