León's dry season runs from November to April, and these are the most comfortable months to visit. Temperatures are high year-round — expect 30–35°C in the day — but the lack of humidity and afternoon rain makes the dry season far more pleasant for walking and volcano hiking.
The rainy season (May–October) brings daily afternoon downpours that turn the streets muddy and make volcano hiking unpleasant. That said, the landscape turns vivid green and the city is emptier. Accommodation is cheaper and the heat is slightly tempered.
The Semana Santa (Holy Week before Easter) and the Fiestas Patrias in September are lively times to be in León, with processions, fireworks, and street parties. The Festival de Música y Arte in November, when it runs, brings performances to the colonial buildings and plazas.