Frozen spinach can be thawed in the refrigerator, in water or in the microwave. Spinach should be thawed at 40 degrees Fahrenheit or less in the refrigerator and at less than 70 degrees in water.
Frozen spinach should be partially thawed before cooking. The fastest way to thaw spinach when it needs to be cooked or served immediately is in the microwave. Thawing spinach in the refrigerator takes the longest, and it can take longer if placed in a colder part of the refrigerator. Spinach can also be thawed under cold running water in a sealed bag or immersed in cold water. Spinach should never be thawed under warm water or at room temperature.