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.
he water gets cold sitting in the pipes/plumbing. To get a good warm/hot wash in this case you could run the machine to fill first (until water hot enough) then set it to spin or drain to drain out the cold water. Then start filling again. This would be for heavily soiled items.
Remember we need thermal energy along with chemical energy (detergent) and mechanical energy (washing action of machine). 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.