The dry season from November to April is the best time to visit San Pedro. Mornings are clear, the lake is calm, and the volcano hike offers summit views without cloud cover. December and January are peak season — more travellers, but still far quieter than major tourist centres.
The rainy season from May to October brings heavy afternoon downpours, which clears early enough most mornings for outdoor activities. Kayaking and swimming are still fine if you start early; the Xocomil wind picks up in the afternoons regardless of season. Vegetation is greener and the town is quieter during the rains, with noticeably lower prices at guesthouses.
The feast of San Pedro Apóstol on 29 June is the biggest local celebration of the year, with processions, marimba, and dancing that run for several days. Semana Santa (Holy Week before Easter) brings Guatemalan visitors to the lake in numbers.