Under the influence of increasing air temperatures, dormant seeds of wetland plants and eggs of microfauna may be subjected to increased sediment temperatures that adversely affect their capacity to germinate or hatch, while the wetland is in its ‘dry’ phase. We conducted a mesocosm experiment to investigate the influence of sediment temperature on the emergence capacity of dormant seeds and eggs. Dry wetland sediment was exposed to temperatures ranging from –180 to 150°C. After re-wetting, the taxon richness and abundance of communities that developed were assessed. Both aquatic plants and microfauna emerged from the seed bank at sediment temperatures lower than 50°C. However, the composition of the microfaunal community was altered once temperatures exceeded 40°C and germination of aquatic plants ceased once temperatures exceeded 50°C. These results suggest that changes to sediment temperature during the dry phase of wetlands may play an important role in influencing communities of wetland aquatic plants and microfauna. Modelled sediment temperature data indicated that minimum sediment temperature could exceed 40°C for extended periods of time under existing climate-change scenarios by 2070. An increase in the occurrence and duration of such temperatures may threaten the abundance and diversity of wetland microfauna and aquatic-plant communities.