Here we present the data of the study by Strobel et al. (2020; doi:10.1016/j.scitotenv.2020.137045), who analysed topsoil samples from South Africa for their compound-specific hydrogen isotopic composition of leaf wax-derived n-alkanes (δ2Hn-alkane) and oxygen isotopic composition of hemicellulose-derived sugars (δ18Osugar). Apparent fractionation, which is the difference between δ2Hn-alkane and the isotopic signature of growing season precipitation δ2Hp (εapp 2H) and δ18Osugar and δ18Op (εapp 18O), was calculated. Coupling both δ2Hn-alkane and δ18O sugar using a 'paleohygrometer' approach enables the calculation of the plants-source water and relative humidity. For more details see Strobel et al. (2020; doi:10.1016/j.scitotenv.2020.137045).