Climate has a profound influence on the most fundamental properties of Texas bays and estuaries: their water temperatures and salinities, their circulation, and even their locations and spatial extents. With climate change, these influences will evolve and possibly change the character of bays and estuaries. Key climate changes include warmer temperatures, changes in amount and distribution of precipitation, and sea level rise. Inflows to Texas bays and estuaries are not altered solely by climate change, but it is possible to infer the impacts attributable to climate change. Specifically, hydrologic model simulations driven by downscaled climate model projections tend to predict roughly equal chances of increases or decreases in total inflows, but with a clear tendency for more erratic inflows as the wettest months get wetter and the driest months get drier. Projections of most hydrological variables have largely spread across models, indicating that change is likely, but the specific magnitude of change cannot be discerned at this time. Both increasing variability and a long-term trend imply that estuarine ecosystems must be able to adapt to a broader range of conditions than those found historically. Management decisions should allow for a range of possible future climate impacts.