Warming milk and water for yeast is a vital step within the baking course of, because it permits the yeast to activate and start feeding on the sugars within the liquid. The perfect temperature for warming the milk and water is between 105-115F (40-46C). At this temperature, the yeast will probably be most energetic and can produce essentially the most fuel, which is critical for the dough to rise.
If the milk and water are too chilly, the yeast is not going to activate correctly and the dough is not going to rise. If the milk and water are too scorching, the yeast will probably be killed and the dough is not going to rise. Subsequently, you will need to use a thermometer to make sure that the temperature is right.