Rainfall is vital for crop production under the rainfed farming systems of Eastern and Southern Africa.

Standard Precipitation Index (SPI) is a meteorological drought indicator based only on precipitation amounts, which allows comparison of rainfall deficits at multiple time and spatial scales. Jayanthi and the FEWS NET team (2013) calculated monthly SPI from monthly satellite rainfall estimate values (NOAA RFE2) across southern Malawi and related that information to district-level maize yield data for 24 years. SPI was used in this study as a drought hazard index for the months corresponding to the silk, tasselling, milk, grain-filling, and hardening phases, namely January-March. These linear equations for single months and multiple months were compared. The analysis shows that maize yield reductions for three types of varieties—local, hybrid, and composite—are best correlated with SPI drought conditions (less than 0.2) in February and March, probably because this is during the grain formation and filling stages. The February SPI is the most relevant index to use as an early warning of drought, as March SPI would come too late to be useful. Due to the variability in rain onset date and the use of monthly data, this study should be repeated in more detail with actual annual start of rain dates and daily or decadal (10-day period) data. The district-wide relationships of drought (SPI) to maize yield reduction were up-scaled to obtain a regional maize vulnerability model for southern Malawi. data to illustrate the characteristics of rainfall patterns and variability both between and within seasons, as these are of importance to farmers. They calculated weather-induced risk associated with the inter- and intra-seasonal variability of rainfall. They found no simple trends at this Moorings station in daily rainfall data, but monthly rainfall analysis gives good indications of four important points: (1) there is no evidence of climate change that would suggest farmers should change practices; (2) this means that long-term records can be used to compare the probability of success of different cropping strategies; (3) calculations of standard deviation for three successive 30-year periods indicated that there is no change in variability of monthly rainfall; (4) when using a fitted statistical model the trend was not statistically significant. This lack of evidence of a trend suggests either that there is no change or that the large variability makes it difficult to detect, even using this long-term dataset. The observed variability of monthly rainfall totals is due to variability in the number of days with rain as well as variability of rainfall amounts on those days. Thus, when there is high variability in rainfall amounts across years, it can be perceived as changing even when there is no statistical trend present. Stern and Cooper conclude that the chance of rain has not remained constant over 89 years, but the trend cannot be explained in a simple manner, as there is no evidence that it was seasonally dependent. When considering the amount of per rain day, there was some indication (though still inconclusive) of a slight increase in mean per rain day (p = 0.015) over the past 40 years. Secondly, almost all the variability in rainfall is inter-annual, so rainfall has always been extremely variable from year to year, and the possible trends may not be new. Therefore, farmers have always had to cope with this variability and adapt their cropping systems. This means that it is vitally important that they are assisted in making farming decisions that are based on good scientific evidence and predictions for each cropping season. and clay), via evapotranspiration (ET), together with the rainfall. Effects of dry spells on crop growth are strongly dependant on soil type and development stage of the crop that is included in seasonal progression of ET. This study showed that maize on sandy soil (particularly during short rains) experienced more and longer water stress periods compared to that grown on a clay soil where there were fewer stress periods during both flowering and grain-filling stages due to available stored soil water. The negative impact of dry spells on yields proved to be higher when analysed on the basis of crop development stages than when analysed on a seasonal basis only, as the occurrence of dry spells affecting yields negatively were highly dependent on soil water storage capacity (Barron et al., 2003). intervals after the start of rains, then flowering is spread over a longer period, decreasing the risk of crop failure due to a midseason dry spell. Drought-tolerant crops (such as sorghum and millet) also have different mechanisms and water-stress levels when their stomata close, so they can produce a yield while using less water through to maturity. The water-harvesting methods described above also will help to accumulate more water during the rainy periods, allowing the crop to continue longer between the rains and into the dry spells. All of these interventions, used alone or in combination, can limit the effects of dry-spell droughts during a growing season.