Why should eggs be refrigerated?
Temperature fluctuation is critical to safety. With the concern about Salmonella, eggs gathered from laying hens should be refrigerated as soon as possible. After eggs are refrigerated, they need to stay that way. A cold egg left out at room temperature can sweat, facilitating the movement of bacteria into the egg and increasing the growth of bacteria. Refrigerated eggs should not be left out more than 2 hours.
Shell Eggs from Farm to Table | USDA Food Safety and Inspection Service
How are eggs transported safely to stores?
The U.S. Department of Commerce's 1990 Sanitary Food Transportation Act requires that vehicles be dedicated to transporting food only. On August 27, 1999, FSIS made effective a rule requiring:
Shell eggs packed for consumers be stored and transported under refrigeration at an ambient (surrounding) air temperature not to exceed 45° F;
All packed shell eggs be labeled with a statement that refrigeration is required; and
Any shell eggs imported into the United States, packed for consumer use, include a certification that they have been stored and transported at an ambient temperature of no greater than 45° F.
Egg Safety Center