Milk typically can be left out at room temperature for about two hours before spoiling. The rate of milk spoilage at room temperature depends upon how much milk is in the container and how cold the milk is when removed from cold storage. In some instances, spoilage occurs after the two-hour mark.
Ideally, milk is stored at 35 degrees Fahrenheit. The overall shelf life of milk decreases by 50 percent for every 5 degrees over 40 F it is kept. The flavor of milk is at its peak when served between 35 F and 40 F. Although it may not be spoiled, the taste of milk degrades after being exposed to a temperature above 40 F for as short a period as 10 minutes.