Abstract Despite the intriguing correlation between continental flood basalt provinces and environmental crises, little is known about how the local/regional sedimentary systems and environment respond to flood basalt volcanism. Active sedimentary systems, and their interaction with volcanism, provide an important rock record to understand palaeoenvironments in volcanic settings. The Paraná–Etendeka Igneous Province is a well-known example of a continental flood basalt emplaced on a dry desert environment, but evidence has also shown the existence of humid conditions during the volcanic episode. This work describes and interprets non-volcanic sedimentary and volcaniclastic rocks interbedded with Paraná–Etendeka Igneous Province lavas in southernmost Brazil to better understand the palaeoenvironmental process and changes during the onset of volcanism. Non-volcanic sedimentary rocks record the existence of ephemeral sheet-like flows and ponds/lakes while volcaniclastic rocks document hydromagmatic activity, supporting a change to more humid conditions. Stratigraphic constraints indicate that this change started with the onset of volcanism and affected the whole province. We suggest that SO 2 degassing from the Paraná–Etendeka province may have caused a net global surface cooling, resulting in precipitation redistribution and a local increase in rainfall. This hypothesis may help explain the cooling and increased humidity observed elsewhere to be closely related to the Paraná–Etendeka emplacement.