Harvest your apples before the temperature drops below 30 degrees F.

Cold temperature injury of apples results in the formation of ice crystals in the spaces between the cells.  When this occurs the cells may die.  A common symptom of freeze damage is seen in the photo below.  This photo is courtesy of Washington State University.

The temperature at which apples suffer freeze damage ranges from 27.3 to 29.4 F depending on variety for an average of 28.4 F. I would suggest apples be harvested and stored in a frost proof area if the temperature is forecast to go below 30 degrees F. 

If you are unable to pick the fruit when temperatures below 30 F. are forecast, as may occur with later ripening varieties, wait until the apples have thawed before harvesting and/or handling.  This will limit the extend of the damage.