The best time to visit Switzerland for sightseeing and to experience the scenic beauty and varying colours is the summer season (June to September) as the mountain passes are open and you can see the most picturesque and panoramic views at this time of the year.
Autumn is a good time for hiking in the Swiss Alps as the view from the mountain peaks can take your breath away. The temperature starts to fall around this time of the year and the air gets cooler.