Viterbo's climate is characterized by mild winters, with temperatures ranging from just above freezing in January and December to as high as 18°C in February. Spring brings a gradual warming trend, with April and May temperatures rising steadily towards the summer highs. Summer months are warm but not hot, with average highs around 25-26°C from June to August. Autumn sees temperatures drop significantly, returning to winter-like conditions by November, before a final push upwards into December's mild finish.