A warmer climate may result in lower thermal efficiency and reduced load-including shutdowns-in thermal power plants. Focusing on nuclear power plants, we use different European datasets and econometric strategies to identify these two supply-side effects. We find that a rise in temperature of 1 degrees C reduces the supply of nuclear power by about 0.5% through its effect on thermal efficiency; during droughts and heat waves, the production loss may exceed 2.0% per degree Celsius because power plant cooling systems are constrained by physical laws, regulations and access to cooling water As climate changes, one must consider measures to protect against and/or to adapt to these impacts.