Spring and early autumn are the best times for walking and cycling in the Geul valley. The landscape is at its best and the town is busy but not overwhelmed. Summer is peak tourist season and the pedestrian centre gets crowded, particularly on Dutch and German public holidays.
Winter has its own appeal: Valkenburg's famous Christmas market, held inside the Fluweelengrot and in the castle caves from November through December, is one of the more atmospheric festive markets in the Netherlands. The Amstel Gold Race cycling classic passes through in April — if you care about professional cycling, this is worth planning around.