The best time to visit Patras is February for the carnival, or May–June and September for the most comfortable all-round weather.
February (Carnival season): If the Patras Carnival is your goal, this is the unmissable window. The three-week festival peaks in the final weekend before Clean Monday (Shrove Monday), with the Grand Parade on the last Sunday drawing the biggest crowds. Book accommodation months in advance.
May–June: Warm and sunny (22–27 °C) with the sea warming up by late May. Crowds are manageable, prices are reasonable, and day trips to Olympia and the surrounding region are ideal.
July–August: Peak summer brings heat (30–35 °C), busy ferry terminals, and higher prices. The city's lively nightlife is at its height, but it can be uncomfortable for sightseeing in the middle of the day.
September–October: Often considered the sweet spot — the sea is warm, temperatures drop to the mid-20s, and the summer crowds thin out. The Patras International Festival continues through September with outdoor concerts and theatre.
November–April (outside carnival): Mild but occasionally rainy. The city is quiet, prices are low, and you'll experience Patras as the Greeks do. Worth considering for visitors primarily interested in Olympia or archaeological sites.