The discovery of a tusk and a rib of a straight-tusked elephant within layer 13 II-2c3 of the famous Lower Palaeolithic archaeological site Schöningen (district Helmstedt, Lower-Saxony, Germany) provided the reason for studying the climatic and ecological conditions of this part of the Middle Pleistocene Reinsdorf sequence in high resolution in relation to new chronometric data. Sediment, pollen, aquatic microfossil (diatoms, ostracods, gyrogonites of charophytes) and micro mammalian analyses provide evidence for a strong environmental change and landscape opening following the post-temperate boreal forest phase of the Reinsdorf Interglacial. Palynological and palaeontological evidence from this horizon suggest increasing dryness and seasonality. The high proportions of non-arboreal pollen including Poaceae as well as a major decrease of thermophile tree taxa indicate the development of zonal steppe environments. The assemblage of small mammal remains includes indicators of temperate as well as cold climatic conditions. A bone tool together with flint artefacts clearly show the presence of hominins in this context. Based on palaeoecological evidence and new luminescence dating, previous correlations of the Reinsdorf sequence to Marine Isotope Stage (MIS) 9 and thus of the interglacial sediments to MIS 9e are confirmed and the onset of the first post-interglacial steppe phase represented by layer 13 II-2c3 to MIS 9d is proposed.