A chemical mechanical polishing system includes a platen to support a polishing pad having a polishing surface, and a pad cooling assembly. The pad cooling assembly has an arm extending over the platen, a nozzle suspended by the arm and coupled to a source of coolant fluid, the nozzle positioned to spray coolant fluid from the source onto the polishing surface of the polishing pad, and an opening in the arm adjacent the nozzle and a passage extending in the arm from the opening, the opening positioned sufficiently close to the nozzle that a flow of coolant fluid from the nozzle entrains air from the opening.