An objective determination of the onset and cessation of the Belg rains of Ethiopia is important for agricultural applications as well as to enhance our understanding of the interannual variability of the rains of the season. Based on a quantitative study of daily rainfall data for 80 stations, we developed, the mean onset and cessation dates, and dry spells. The spatial and temporal variability of the onset and cessation dates are assessed and examined by testing different onset and cessation definitions for sample stations from the Belg -growing areas.

The study shows that there is more variability in the onset of the Belg rains than in its cessation. The highest variability in the onset was over the Northeastern and some places of central Ethiopia. The cessation dates of the Belg season have highest coefficient of variation over western, southwestern and west part of central Ethiopia.

The dry spell analysis shows that eastern, southeastern, northeastern and northwestern Ethiopia have long dry spell lengths in the Belg season.