In the coming days, the Sahara, one of the driest places in the world, will experience the heaviest rains in at least 30 years.

A rare atmospheric setup could bring pockets of flooding to parts of Chad, Libya, Niger and Algeria. Half the Sahara receives less than an inch of rain annually. Sand dunes are poor absorbers of excess runoff, making flooding possible even with rain totals that seem relatively low compared to other parts of the world.

The WeatherRadar shows rain forecasted to fall in the Sahara in early September. In just a few days, rainfall amounts 30-50 times greater than usual for September are expected in some places. In some areas, rainfall totals may amount to what would typically fall in a few years.

This unusual precipitation is caused by the Intertropical Convergence Zone (ITCZ), an area around the equator where the trade winds from the northern and southern hemispheres meet. With the ITCZ moving further north than usual, rain is expected to fall in typically dry areas in the Sahara.