Sacred Valley in September

May through September brings dry season — clear skies, crisp mornings, and perfect conditions for hiking between ruins. July and August see the most crowds but also the most reliable weather. June hits the sweet spot with fewer tourists and still-dry conditions. The wet season from December to March turns the valley emerald green but brings afternoon downpours that can wash out roads. October and April are shoulder months with mixed weather but fewer crowds and lower prices. Here's what nobody tells you: even dry season gets rain occasionally, and even wet season has gorgeous sunny mornings. Pack layers regardless of when you visit — valley mornings start cold, afternoons get warm, and evenings turn chilly again. The altitude means intense sun year-round, so bring sunscreen and a hat.