An hourly optimization strategy to enhance dew-point indirect evaporative coolers is presented. First, the performance of the system throughout a year is modeled and then, using the hourly values of input parameters, a multi-objective optimization is done at each hour. Four diverse climatic conditions in the world, in which the system is the best cooling option, are studied while operating cost, the coefficient of performance, and water consumption are selected as the objective functions. Inlet air velocity and working to air ratio are considered as the decision variables while all the necessary constraints like meeting thermal comfort are taken into account. A previously optimized design is selected and the potential for further improvement of the system is evaluated for that design. The hourly, monthly, and annual results are presented and discussed. The obtained results reveal the huge improvement potential of the hourly optimization strategy so that it enhances the objective functions 17.8, 19.6, and 36.2% on average in the four investigated climatic conditions. Besides, as discussed thoroughly in the paper, because the hourly optimization strategy has the ability to be applied for every single design of dew-point indirect evaporative coolers in both design and retrofit stages, the introduced method is a general approach.