San Juan del Río's highland climate is temperate year-round — warm days and cool nights, no extreme heat or cold. The dry season runs from November through May. The rainy season (June through October) brings afternoon showers but the air is cleaner and the surrounding landscape greener.
The Feria de San Juan in late June is the city's main festival, with a market, music, and the regional opal trade concentrated into a few busy days. Semana Santa draws pilgrims to the colonial churches. October brings the grape harvest in the nearby vineyards, and some haciendas open for tastings and events.