The permitted temperature increase is usually in the range of 1.5-3 ®C, and maximal water temperature at the outlet should be less than about 30 °C. Adverse weather conditions, such as unusually high water temperature, might require reduction of the electrical output of the NPP, due to reaching the limits of outlet water temperature. Very hot summer conditions caused the power reduction of several American, French, German and nuclear power plants during the summer of 2010.