The county lies between the altitude of 400m and 1800m above sea level. The central part of the county is characterized by hilly ridges separated by wide low lying areas and has slightly lower elevation of between 600m and 900m above sea level. The highest areas in the county are Kitui Central, Mutitu Hills and Yatta plateau. Due to their altitudes, they receive more rainfall than other areas in the county and are the most productive areas. To the eastern side of the county, the main relief feature is the Yatta plateau, which stretches from the north to the south of the county and lies between rivers Athi and Tiva. The plateau is characterized with plain wide shallow spaced valleys.
Like other regions of Kenya, population dynamics form an integral part of socio- economic and cultural development. The county’s populations was 1,012,709 according to 2009 population and household census report of which 531,427 were females while 481,282 were males and is expected to grow to 1,077,860 in 2012. The population growth rate of the county at 2.1% is slightly lower than the national rate of 2.6%.
The county can be divided into four agro-ecological zones. These include: Semi-Arid farming zone, Semi-arid ranching areas, Arid-Agro-pastoral area and Arid-Pastoral Zone. Semi- Arid Farming Zone has good potential for agricultural development and is currently either cultivated or under woodlands. The Semi-Arid Ranching Areas are less fertile and are currently used for drought resistance crops and livestock keeping. The Arid-Agro-Pastoral areas are generally suitable for grazing. Finally, the Arid-Pastoral Zones are suitable for rearing of livestock.
The climatic condition varies across the county in terms of rainfall and temperature.The rainfall pattern is bi-modal with long rains falling in the months of March to May. These are usually very erratic and unreliable rainfall. The short rains which form the second rainy season fall between October and December and is abit reliable. The county experiences high temperatures throughout the year, which ranges from 140c to 340c. The hot months are between mid- July & September and January & February. The maximum mean annual temperature ranges between 260 C and 340 C whereas the minimum mean annual temperature ranges between 140 C and 220 C.
The county comprises of 16 administrative sub counties namely; Kitui Central, Lower Yatta, Kitui West, Kisasi, Nzambani, Mutitu, Mutomo, Ikutha, Katulani, Matinyani, Mwingi Central, Mwingi East,Tseikuru, Muumoni, Kyuso and Migwani.The county is further divided into 41 divisions, 152 locations and 404 sub locations