Heavy Rainfall Associated with the July-August Season over the Central Rift Valley of Kenya

Volume 8:1
Okoola*, R. E. and Gitau W.* Shilenje**,Z. W. and Camberlin*** P.
*University of Nairobi, Kenya** Kenya Meteorological Department, Kenya*** Climate Research Centre, France
Corresponding author
Okoola*, Raphael.E. A.
University of Nairobi, P.O.Box 30197-00100,Nairobi
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.


Two rainy seasons are recognized over Kenya. These are the long rainy season March to May (MAM) and the short rainy season of October to December (OND). During these seasons the whole country experiences rainfall. However, over the central Rift Valley, the second rainfall season seems to be missing. This is due to the escarpments over the region with the shift of the short rains such that the July to August rainfall becomes a dominant season. During this season, the heating zone has generally shifted to the north of the equator. Orographic rainfall is generally prevalent during the months of July and August.
Orographic rainfall in the tropics is not common. It occurs mainly in July-August when the dynamic low lies over the region and the escarpments lift the westerly winds over the region bringing with them the moisture laden Congo air mass. They occur during the low pressure season with the plateau lifting the moist air (in the dynamic low) with the ITCZ far to the north of the equator. It is then observed that the moisture laden Congo air is lifted over the escarpments bringing rainfall over the region.
Full Text:
Download Full Text (pdf)

Get In Touch

Physical Address: Kenya Meteorological Department (KMD) Dagoretti Corner along Ngong Road, next to the Institute for Meteorological Training and Research (IMTR) Library.
Postal Address: P. O. BOX 41959 - 00100
Nairobi, Kenya

Mobile: +254 71 708 9394

Phone 1: +254 20 214 7770

Phone 2: +254 20 386 7880

Fax:     +254 20 387 6955

Email 1:,

Email 2: