Dry season

The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year. The tropical rain belt lies in the southern hemisphere roughly from October to March, and during this time the northern tropics experience a dry season in which precipitation is more rare, and days are typically sunny throughout. From April to September, the rain belt lies in the northern hemisphere, and the southern tropics experience their dry season.

Data shows that in Africa, the advent of the Dry Season coincides with a rise in the cases of measles--which researchers believe might be attributed to the higher concentration of people in the dry season, as agricultural operations are all but impossible without irrigation. During this time, some farmers move into cities, creating hubs of higher population density, and allowing disease to spread more easily.