The
dry season is a yearly period of low rainfall, especially in the
tropics. The weather in the tropics is dominated by the
tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The tropical rain belt lies in the southern hemisphere roughly from October to March; during that time the northern tropics have a dry season with sparser
precipitation, and days are typically sunny throughout. From April to September, the rain belt lies in the northern hemisphere, and the southern tropics have their dry season. Under the
Köppen climate classification, for
tropical climates, a dry season month is defined as a month when average precipitation is below .