Geography of Brazil latitude), which crosses the country at the latitude of the city of São Paulo. Brazil has five climatic regions: equatorial, tropical, semiarid, highland tropical, and subtropical. Temperatures along the equator are high, averaging above , but not reaching the summer extremes of up to in the temperate zones. There is little seasonal variation near the equator, although at times it can get cool enough for wearing a jacket, especially in the rain. At the country's other extreme, there are frosts south of the Tropic of Capricorn during the winter (June–August), and there is snow in the mountainous areas, such as
Geography of Nigeria known as the harmattan. The northward retreat of the tropical continental airmass (CT), is caused by the sun's northward shift from the tropic of capricorn in the southern hemisphere to the tropic of cancer in the northern hemisphere. This shift begins from February and ends in June, when the sun is fully overhead, at the tropic of cancer in the northern hemisphere. During this northward migration of the sun as a result of the earth tilting along its axis, the sun crosses the equator (around March), moving over west Africa at this time on its journey to the northern hemisphere.