The hydrogen isotopic composition of leaf wax-derived n-alkanes (δ²H_n-alkanes) is a widely applied proxy for (paleo)climatic changes. It has been suggested that the coupling with the oxygen isotopic composition of hemicellulose-derived sugars (δ¹⁸O_sugar) - an approach dubbed ‘paleohygrometer’ – might allow more robust and quantitative (paleo)hydrological reconstructions. However, the paleohygrometer remains to be evaluated and tested regionally. In this study, topsoil samples from South Africa, covering extensive environmental gradients, are analysed. δ²H_n-alkanes correlates significantly with the isotopic composition of precipitation (δ²H_p), whereas no significant correlation exists between δ¹⁸O_sugar and δ¹⁸O_p. The apparent fractionation (ε_app) is the difference between δ²H_n-alkanes and δ²H_p (ε_{app 2H}) and δ¹⁸O_sugar and δ¹⁸O_p (ε_{app 18O}), respectively, and integrates i) isotopic enrichment due to soil water evaporation, ii) leaf (and xylem) water transpiration and iii) biosynthetic fractionation. We find no correlation of ε_{app 18O} nor for ε_{app 2H} with temperature, and no correlation of ε_{app 2H} with potential evapotranspiration and an aridity index. By contrast, ε_{app 18O} correlates significantly with both potential evapotranspiration and the aridity index. This highlights the strong effect of evapotranspirative enrichment on δ¹⁸O_sugar. In study areas without plant predominance using Crassulacean Acid Metabolism (CAM), coupling δ¹⁸O_sugar and δ²H_n-alkanes enables to reconstruct δ²H_p and δ¹⁸O_p with an offset of Δδ²H = 6 ± 27‰ and Δδ¹⁸O = 0.8 ± 3.7‰, respectively, as well as relative humidity (RH) with an offset of ΔRH = 6 ± 17%. The paleohygrometer does, however, not work well for our study areas where CAM plants prevail (reconstructed δ¹⁸O_p, δ²H_p and RH are off by 3.1‰, 27.2‰ and 31.7%). This probably reflects plant-specific (phenological) adaptations and/or post-photosynthetic exchange reactions related to CAM metabolism. Overall, our findings corroborate that δ²H_n-alkanes and δ¹⁸O_sugar are valuable proxies, and the paleohygrometer is a promising approach for paleoclimate reconstructions in southern Africa.