The ideal temperature for a refrigerator is 40 degrees Fahrenheit or below, according to the U.S. Food and Drug Administration (FDA) . This temperature inhibits the growth of microorganisms that can cause foodborne illnesses, such as salmonella, listeria, and E. coli. However, Consumer Reports suggests that a fridge temperature of 37° F will keep fresh food good for as long as possible, with no ice crystals on lettuce or bacteria breeding in raw meats. Its important to note that the temperature controls on many fridges only allow you to choose from a series of numbers, usually 1 through 5, with 1 being the coldest and 5 being the warmest. Therefore, its recommended to use a refrigerator thermometer to ensure that the temperature is at or below 40°F.