The best time to visit Rainbow Mountain is during the dry season, which runs from May to September in Peru. The weather is usually clear and dry during this time, with fewer rain and snow chances. The dry season also offers the best visibility for viewing the colorful stripes of the mountain.
However, it is essential to note that Rainbow Mountain has recently become a popular tourist attraction, and crowds can be overwhelming during peak seasons. If you prefer to avoid crowds, it may be best to visit during the shoulder season, which runs from April to May and September to November.
It is also essential to remember that the weather in the Andes can be unpredictable, and it is possible to experience rain or snow even during the dry season. Therefore, it is vital to be prepared with appropriate clothing and gear for all types of weather.