Cyanobacteria development in fresh waters presents a hazard that needs to be adequately managed. Climate change may alter the risk, so it is crucial to understand: (a) how cyanobacteria respond to warming temperatures and (b) how those changes will interact with variation in nutrient availability (representing different future land uses or hydrology). These concepts were explored using a variety of approaches: (a) statistical analysis of data from more than 1000 natural and man-made lakes in United States collected in 2007 by the US EPA; (b) statistical modelling; building a Bayesian network with long term data from 20 lakes located at different latitudes, spanning a variety of trophic states; (c) deterministic modelling; conducting multiple simulations under combined temperature changes and nutrients availability scenarios. The Bayesian network revealed that there is a 5% greater probability of having a bloom in the highly hazardous class with an increase in temperature of 0.8ºC or an increase in TP of 0.01 mgL-1 from oligotrophic to mesotrophic conditions. This provided insights on how cyanobacterial risk may change with temperature and nutrient increases. This knowledge will support the development of strategic adaptation plans by water utilities.