The ideal temperature for a freezer is 0°F (-18°C) or below, according to the United States Department of Agriculture (USDA) and other sources. This temperature creates a deep freeze that inactivates bacteria, yeast, and mold that may be present in the food, keeping it safe to eat for longer periods of time. However, some sources suggest that a range of -1°F to 1°F is still acceptable. It is important not to set the temperature colder than necessary, as this can cause vegetables to lose their freshness. To ensure that the freezer is set to the correct temperature, place an appliance thermometer in the freezer and check it regularly to make sure it stays constant. If the freezer is in a garage or basement, the temperature may need to be adjusted to account for humidity or outside temperatures. It is also important not to put too much food in the freezer, as chilled air must be able to move evenly around the food to keep it frozen. If the power goes out, keep the freezer door closed as much as possible to maintain the temperature. When the door stays closed, a freezer can keep food at an acceptable temperature for around 48 hours.