Sapa’s climate can be classified as sup-tropical, with generally cooler weather than the rest of Vietnam due to its position in the far north as well as its high elevation. The hottest weather arrives in July and August, with temperatures averaging at about 20 degrees Celsius, and high levels of humidity and rain. On the opposite end of the scale, January and February bring temperatures averaging at around 8-9 degrees Celsius, and even occasionally feature snowfall. During winter the area is also prone to fog and mist, which presents a double edged sword for travellers, as while it may detract from the views, it shrouds the town and valley in a gorgeous and deeply mystical air.
Peak tourist season in Sapa runs from June to August, when the weather is at its hottest. The months of April-June and September-November also have generally favourable conditions, and you can expect far fewer tourist crowds during these months. April and May in particular are great months to visit, as the rice fields will all be a bright verdant green, and the same goes for September, when they turn a rich gold as harvest approaches.