In May, the weather in Lạng Sơn is typically hot. Average daily high temperature in May is about 29 degrees above zero. On average, Lạng Sơn has 20 rainy, 4 sunny, 4 partly cloudy, and 3 cloudy days in May. The rains are usually heavy. May as well as June, July, August, and September is considered the most uncomfortable time to visit Lạng Sơn.