Quality of the rainfall season, calculated for a rainfall season from August to July in the following year, based on data from SASSCAL Weathernet and gap-filled with WorldClim historic data (Fick and Hijmans, 2017). The quality of the season is based on criteria developed by Gibbs and Maher (1967) and Botha (1999) and indicated by colour-coding: Brown: extreme drought, precipitation below the 10th percentile (72 mm), light-brown: drought, precipitation below the 40th percentile (131 mm), green: normal, precipitation between the 40th and 70th percentile (131 and 166 mm), blue-green: wet, precipitation above the 70th percentile (166 mm), and blue: extreme wet years, precipitation above the 90th percentile (220 mm). The stippled line represents the long-term median rainfall (137 mm). (The slight differences to the neighbouring observatory S10 stem from the fact that the long-term values are based on WorldClim data, and the observatories fall on different cells within this data set.)

The SPEI index is a standardised monthly climatic balance computed as the difference between the cumulative precipitation and the potential evapotranspiration (Vicente-Serrano et al. 2010). For this presentation the SPEI value per month is based on the accumulated values of the previous 12 months. Red bars indicate drought, blue bars humid conditions.