There are also minor variations due to mountainous terrain and elevation. Figure 3 shows the same data for a coastal climate in the city of Jeddah, located on the Red Sea in southeastern Saudi Arabia. In order to better calibrate the reader, we searched for a climate similar to these in the United States. As for precipitation, we see that all of these cities receive little rainfall - even as little as 100 mm per year. During the months of January to May, the average is about 25 mm per month, while after May precipitation is negligible.
Relative humidity is low, and the potential evaporation is greater than precipitation.
As mentioned above, rains are infrequent, but occur in the winter during strong storm activity. Also during the winter months, the region is susceptible to cyclones, which travel from the Mediterranean through this region to India. ENSO events figure into the prevailing global conditions that make the Middle East so arid. The West Coast of Africa where Nigeria located received highest precipitation in this continent, up to more than 100 inches per year. Precipitation decreases with latitude as one approach the dry belt of the two hemisphere.