Lang Son's climate is characterized by distinct seasonal patterns. The coolest period is during the winter months of January and December, with temperatures ranging from 2-27°C and 5-26°C respectively. Spring brings a gradual warming trend in February to April, with temperatures rising to an average high of 34°C. Summer months of May to August are hot and humid, with temperatures often reaching 38°C. Autumn sees a return to milder conditions in September to November, before the winter chill sets back in.