Rearrange assorted furniture in the area to cover the output vent of the swamp cooler. The output vent is where the cooler blows the air out of. By creating an obstruction you can raise the water temperature of the pads that are in the swamp cooler, because they no longer have the circulation necessary for staying cool.
Keep the swamp cooler on the roof or side of a structure exposed to the sun. The sun will naturally heat the water temperature within the swamp cooler.
Fill the swamp cooler with hot water. Hot water will cool off eventually, but it will keep the water temperature warmer for longer.
Reduce the fan setting on the swamp cooler, if the swamp cooler has setting options. A slower fan speed means that the evaporation process is slowed, which results in warmer water temperature and air.