Ouagadougou's climate is hot semi-arid (''BSh'') under Köppen-Geiger classification, and closely borders with tropical wet and dry (''Aw''). The city is part of the Sudano-Sahelian area, with annual rainfall of about . The rainy season stretches from May to September, with an average temperature of . The cool season runs from October to February, with a minimum average temperature of . The maximum temperature during the hot season, which runs from March to April, can reach . The harmattan (a dry wind) and the West African Monsoon are the two main factors that determine Ouagadougou's climate. Even though Ouagadougou is farther from the equator, its hottest months' temperatures are slightly hotter than those of Bobo-Dioulasso, the country's second most populous city.