Spring (April-May) and autumn (September-October) are the most comfortable seasons in Serres. Spring brings wildflowers to the surrounding hills and is the best time for Lake Kerkini birdwatching. Autumn is dry and warm, and the forest around Lailia turns gold in late October.
Summer (July-August) is hot, with temperatures regularly above 35°C; the city empties as locals leave for the coast. Winter is cold, with occasional snow, and the small ski centre at Lailia opens in good years. The festival of Anastenaria at the nearby village of Agia Eleni on 21 May -- one of the most extraordinary folk traditions in Greece, in which participants dance barefoot over hot coals while holding icons of Saints Constantine and Helena -- is worth timing a visit around.