April through June and September through October are the best months for Vilafranca and the Camino Frances. Temperatures in the valley are mild — warm enough to walk in shirtsleeves, cool enough to sleep without difficulty — and the light in the mornings is remarkable. Spring brings the chestnuts and oaks into leaf along the mountain approaches; autumn turns the vineyards gold just before the harvest. The hostels have space, the restaurants are open, and the town feels alive without being overwhelmed.
July and August are hot in the valley — temperatures regularly reach 32°C or above — and the Camino is at its most crowded. The final stage from Vilafranca over the O Cebreiro pass into Galicia is hard work in summer heat, and the albergues in town fill early. If you are walking, start before 7am and be in your bunk by early afternoon. September brings relief: the harvest begins in the vineyards around town, the Fiesta del Cristo de la Esperanza fills the streets with the town's own celebration rather than purely pilgrim traffic, and the mountain light turns copper and clear. October is the wine harvest proper — the bodegas are busy, the air smells of fermenting must, and the Camino returns to something closer to its older, quieter self.