Lyon is situated in an area of France that's subject to several important climatic influences. The Alps can send pockets of cold air down the Rhone Valley to the city, but these mingle with the warm Mediterranean breezes. In general, the climate is temperate, fairly hot in the summer and relatively cold in the winter. Heavy precipitation is a dominant aspect of the city's weather, and you can expect rain in Lyon year-round: heavy thunderstorms in summer, gray days and downpours in autumn, flurries of snow and biting sleet in winter, and short, fresh showers in spring.
June-September temperatures frequently reach (and exceed) 85 F/30 C, and despite the warning about precipitation, summer is usually hot and sunny. Winter temperatures tend to stay just above freezing, but there are some bitterly cold, windy days. Spring and fall temperatures range 50-60 F/10-15 C, with especially fine days reaching up to 65-70 F/18-20 C.