This paper assesses the impacts of observed and projected climate changes on key indicators and critical thresholds for grape growth and wine production across the three appellations of origin in Ontario (Canada). The historical analysis is based on local weather station data from Environment Canada and the projections are based on selective ensembles of seasonal global climate model projections, statistically downscaled to create local-daily climate change scenarios. Average growing season temperatures have already been warming and growing degree days are increasing, both at statistically significant rates, and are both projected to continue increasing over the course of the twenty-first century. For Niagara Peninsula and Lake Erie North Shore, these one-time cool climate wine regions have already evolved into intermediate climate wine regions and are projected to transition into warm or even hot climate regions by the 2080s. There is also evidence showing that heat stress has and will likely continue to increase, while freeze damage has and likely will continue to decrease. Pruning and shading are the key short-term adaptation strategies while varietal selection is the key long-term adaptation strategy to minimize risks and maximise opportunities in response to these observed and projected regional climate change impacts.