Preheat processes for a millisecond anneal system are provided. In one example implementation, a preheat process can include receiving a substrate on a wafer support plate in a processing chamber of a millisecond anneal system; obtaining one or more temperature measurements of the wafer support plate using a temperature sensor; and applying a preheat recipe to heat the wafer support plate based at least in part on the temperature of the wafer support plate. In one example implementation, a preheat process can include obtaining one or more temperature measurements from a temperature sensor having a field of view of a wafer support plate in a millisecond anneal system; and applying a pulsed preheat recipe to heat the wafer support plate in the millisecond anneal system based at least in part on the one or more temperature measurements.