Tropical grasslands experience hot weather in every season. In the winter, a mass of dry, sinking air covers some savanna lands. This causes the winter to be a rainless and relatively hot season. Temperatures can be well over 64° F (18° C) during the winter. The summer, however, is considered the rainy season. Rain clouds form over the savanna as warm, moist air arrives from the equator. Temperatures for the summer remain above 80° F (27° C). Savannas that have warm and dry winters and hot, rainy summers are called monsoon climates. Monsoon comes from the Arabic word mauism, meaning season. Monsoon climates experience winds that go in different directions at different times of the year. Although most tropical grasslands are located in the tropics, precipitation in savannas can greatly vary. For instance, some Australian savannas receive only 18 inches (46 centimeters) a year, while African savannas can receive more than three times that. Temperatures can also vary in different savannas, but usually by no more than 20° F (-7° C).