The warm water for your washer is simply a mixture of the hot and cold water available from your home. If the hot water entering the machine isn't very hot, the warm is actually cool. Also, in northern climates, during winter months, the cold water entering the unit may be significantly colder than in the summer, which causes the warm water to be cooler.
In some cases, the water inlet valve may be restricted, or there may be sediment on the screen, that blocks the input of the hot water. For more information, see the Washing Machine Troubleshooting section of our website.