Tropical rainforests occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation value of at least 60 mm – and may also be referred to as lowland equatorial evergreen rainforest. They rarely extend more than 10 degrees north or south of the equator are a sub-set of the tropical forest biome type that occurs roughly within the 28 degree latitudes (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest (or tropical wet forest) that also includes tropical seasonal forests.