Methods for calculating a maximum safe over-rated power demand for a wind turbine operating in non-standard conditions include the steps of determining a value indicative of a risk of exceeding an ultimate design load during operation in a standard operating condition, and establishing a maximum over-rated power demand corresponding to a maximum power that the turbine may produce under the non-standard operating condition without incurring an increased risk of exceeding the ultimate design load, with respect to operation in the standard condition. A method of over-rating a wind turbine, a wind turbine controller, a wind turbine and a wind power plant are also claimed.