On the basis of latitudinal extent, the globe is divided into three broad heat zones.
The Torrid is also known as the Tropics. The zone is bounded on the north by the Tropic of Cancer and on the south by the Tropic of Capricorn; these latitudes mark the northern and southern extremes in which the sun seasonally passes directly overhead. This happens annually, but in the region between, the sun passes overhead twice a year.
In the Northern Hemisphere, in the sun's apparent northward migration after the March equinox, it passes overhead once, then after the June solstice, at which time it reaches the Tropic of Cancer, it passes over again on its apparent southward journey. After the September equinox the sun passes into the Southern Hemisphere. It then passes similarly over the southern tropical regions until it reaches the Tropic of Capricorn at the December solstice, and back again as it returns northwards to the Equator.
In the two Temperate Zones, consisting of the tepid latitudes, the Sun is never directly overhead, and the climate is mild, generally ranging from warm to cool. The four annual seasons, spring, summer, autumn and winter, occur in these areas. The North Temperate Zone includes Europe, Northern Asia, and North and Central America. The South Temperate Zone includes Southern Australasia, southern South America, and Southern Africa.