ITCZ: The Intertropical Convergence Zone

Near the equator, from about 5° north and 5° south, the northeast trade winds and southeast trade winds converge in a low pressure zone known as the Intertropical Convergence Zone or ITCZ. Solar heating in the region forces air to rise through convection which results in a plethora of precipitation. The ITCZ is a key component of the global circulation system.
Weather stations in the equatorial region record precipitation up to 200 days each year, making the equatorial and ITC zones the wettest on the planet. The equatorial region lacks a dry season and is constantly hot and humid.
The migration of the inter-tropical convergence zone (ITCZ) in Africa affects seasonal precipitation patterns across that continent.

ITCZ

From: http://upload.wikimedia.org/wikipedia/commons/d/d7/ITCZ_january-july.png

Seasonal Migration of the ITCZ in Africa 

From: http://people.cas.sc.edu/carbone/modules/mods4car/africa-itcz/index.html