A system configured to decrease the emissions of a power plant system during transient state operation is disclosed. In one embodiment, a system includes: at least one computing device adapted to adjust a temperature of an operational steam in a power generation system by performing actions comprising: obtaining operational data about components of a steam turbine in the power generation system, the operational data including at least one of: a temperature of the components and a set of current ambient conditions at the power generation system; determining an allowable operational steam temperature range for the steam turbine based upon the operational data; generating emissions predictions for a set of temperatures within the allowable steam temperature range; and adjusting the temperature of the operational steam based upon the emissions predictions.