ROCKFORD, Ill. (WTVO) — With thousands of households across northern Illinois currently suffering a power outage due to an ice storm, the safety of items stored in a refrigerator can become an issue.

As of Thursday morning, ComEd says it expects 80% of customers to have power restored by Thursday evening, but says others may not be restored until Saturday.

But, how long can food stay good in a refrigerator when the power goes out?

According to the Centers for Disease Control and Prevention, food will stay safe up to 4 hours in a refrigerator, so long as it hasn’t been opened.

Food will stay good for up to 48 hours in a full freezer, or 24 hours in a half-full freezer.

It is important that the refrigerator door not be opened, though. Food must stay at 40 degrees or below, or else it becomes perishable and must be thrown out.

The CDC says “If in doubt, throw it out!“

Blocks of dry ice or ice can keep food cold in the refrigerator.