A method for determining the temperature of a metal strip (1) inside a cooling apparatus (4) of a hot rolling installation is implemented by an electronic device (12). This method includes acquiring a temperature measure of a strip portion at a current time instant; estimating, at the current time instant, a heat flux extracted from the strip portion inside the cooling apparatus according to a thermal model, and computing a strip portion temperature at a next time instant from the acquired temperature measure and the estimated extracted heat flux. The thermal model models an air cooling of the strip portion, a coolant header cooling of the strip portion by a coolant header and a remaining coolant cooling of the strip portion, wherein for the coolant header cooling the model models both an impingement cooling of the strip portion and a parallel flow cooling of the strip portion.