ORIGINAL PAPER Intra-seasonal rainfall variability during the maize growing season in the northern lowlands of Lesotho Mphethe Isaac Tongwane & Mokhele Edmond Moeletsi Received: 19 December 2013 /Accepted: 23 May 2014 /Published online: 18 June 2014 # Springer-Verlag Wien 2014 Abstract Intra-seasonal rainfall distribution was identified as a priority gap that needs to be addressed for southern Africa to cope with agro-meteorological risks. The region in the northwest of Lesotho is appropriate for crop cultivation due to its relatively favourable climatic conditions and soils. High rainfall variability is often blamed for poor agricultural production in this region. This study aims to determine the onset of rains, cessation of rains and rainy season duration using historical climate data. Temporal variability of these rainy season characteristics was also investi- gated. The earliest and latest onset dates of the rainy season are during the last week of October at Butha-Buthe and the third week of November at Mapoteng, respectively. Cessation of the season is predominantly in the first week of April making the season approximately 137–163 days long depending on the location. Average seasonal rainfall ranged from 474 mm at Mapoteng to 668 mm at Butha-Buthe. Onset and cessation of the rainfall season vary by 4–7 weeks and 1 week, respectively. Mean coefficient of variation of seasonal rainfall is 39 %, but monthly variations are higher. These variations make annual crop management and planning difficult each year. Trends show a decrease in the rainfall amounts but improvements in both the temporal distribution of annual rainfall, onset and cessation dates. 1 Introduction Rainfall in Lesotho and southern Africa is strongly determined by a number of atmospheric circulation patterns (Usman and Reason 2004; Reason et al. 2006a; Davis 2011). The most favourable rainfall conditions over most of the region are provided by tropical temperate troughs extending from the west of the subcontinent forming large-scale bands of clouds (Usman and Reason 2004; Todd et al. 2004; Pohl et al. 2009). However, the occurrence of the Botswana Upper High pres- sure system can result in drought in Lesotho and southern Africa as a whole (Garanganga 2007; Davis 2011). Much of the central and subtropical subcontinent receives more than 60 % of its annual rainfall during the December–February period (Engelbrecht et al. 2009). During winter, the subtrop- ical high-pressure belt is well-established over southern Africa resulting in limited rainfall in Lesotho (Johnsson 2004; Engelbrecht et al. 2009; Engelbrecht and Landman 2010). Winter rainfall is mostly attributed to the transient moisture from the mid-latitude cold fronts originating from the Atlantic Ocean. Lesotho receives approximately 85 % of its total rainfall in summer (October–April) and the remaining 15 % in winter (Ministry of Natural Resources 2000). Lesotho’ s precipitation is characterized by high climate variability from year to year. The dominant climatic mode responsible for seasonal rainfall variability across central southern Africa has been pointed out to be the El-Nino Southern Oscillation (Manatsa et al. 2008). Besides the variability in climate, topography imposes severe constraints on crop production. In Lesotho, the consequences of large variability in climatic conditions and topography have led to great differences in agro-ecological zones (Lowlands, Highlands, Foothills and Senqu River Valley) and agricultural production (Moeletsi and Walker 2013). The lowlands are geographically situated on the western part of the country along the border with South Africa and can be further divided into two parts: northern and southern lowlands. Together with the foothills, the lowlands are areas of higher agricultural potential in the country (Dejene et al. 2011). The northern lowlands are the main agricultural production areas mainly M. I. Tongwane (*) : M. E. Moeletsi Agricultural Research Council, Institute for Soil, Climate and Water, Private Bag X79, Pretoria 0001, South Africa e-mail: tongwanem@arc.agric.za M. E. Moeletsi Risks and Vulnerability Assessment Centre, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa Theor Appl Climatol (2015) 120:575–585 DOI 10.1007/s00704-014-1183-2