A hybrid evaporative cooler system for cooling a process fluid, the hybrid evaporative cooler system comprising: a fan configured to produce an airstream, the fan being located in or connected to an air tunnel or chamber; an evaporative cooler located upstream or downstream of the fan; a cooling coil located upstream or downstream of the fan, and located downstream of the evaporative cooler, and configured to receive the process fluid from a source; and a controller configured to operate the hybrid evaporative cooler system in a wet mode, in which the evaporative cooler is activated to receive a working fluid and to condition the airstream and in which the cooling coil cools the process fluid using the airstream, and configured to operate the evaporative cooler system in a dry mode in which the evaporative cooler is deactivated and in which the cooling coil cools the process fluid using the airstream, the controller further configured to: receive a temperature set point for process fluid leaving the cooling coil; determine a minimum fluid temperature based on a coil performance model, wherein the minimum fluid temperature is the lowest temperature of the process fluid that the cooling coil can deliver at a given ambient temperature or a given inlet air temperature while operating in the dry mode, and wherein the coil performance model is configured to predict the minimum fluid temperature that can be achieved by the hybrid evaporative cooler system in dry mode for any given ambient temperature or any given inlet air temperature under any available operating condition; and operate the hybrid evaporative cooler system in the dry mode on condition that the temperature set point is greater than the minimum fluid temperature. a fan configured to produce an airstream, the fan being located in or connected to an air tunnel or chamber; an evaporative cooler located upstream or downstream of the fan; a cooling coil located upstream or downstream of the fan, and located downstream of the evaporative cooler, and configured to receive the process fluid from a source; and a controller configured to operate the hybrid evaporative cooler system in a wet mode, in which the evaporative cooler is activated to receive a working fluid and to condition the airstream and in which the cooling coil cools the process fluid using the airstream, and configured to operate the evaporative cooler system in a dry mode in which the evaporative cooler is deactivated and in which the cooling coil cools the process fluid using the airstream, the controller further configured to: receive a temperature set point for process fluid leaving the cooling coil; determine a minimum fluid temperature based on a coil performance model, wherein the minimum fluid temperature is the lowest temperature of the process fluid that the cooling coil can deliver at a given ambient temperature or a given inlet air temperature while operating in the dry mode, and wherein the coil performance model is configured to predict the minimum fluid temperature that can be achieved by the hybrid evaporative cooler system in dry mode for any given ambient temperature or any given inlet air temperature under any available operating condition; and operate the hybrid evaporative cooler system in the dry mode on condition that the temperature set point is greater than the minimum fluid temperature. receive a temperature set point for process fluid leaving the cooling coil; determine a minimum fluid temperature based on a coil performance model, wherein the minimum fluid temperature is the lowest temperature of the process fluid that the cooling coil can deliver at a given ambient temperature or a given inlet air temperature while operating in the dry mode, and wherein the coil performance model is configured to predict the minimum fluid temperature that can be achieved by the hybrid evaporative cooler system in dry mode for any given ambient temperature or any given inlet air temperature under any available operating condition; and operate the hybrid evaporative cooler system in the dry mode on condition that the temperature set point is greater than the minimum fluid temperature.