"Thermoplastic insulation may stiffen at temperatures lower than -10°C (+14° F). NEC 402.3" Wire manufacturers recommend exercising caution when unspooling wire in freezing temperatures. Because copper wire memory is more prevalent in colder temperatures, installing cables when the temperature is too cold can damage the conductors PVC jacket during installation. Following are a few thoughts on preparing branch circuit power cables to speed installation and avoid problems. When possible keep the power whips warm, move them into a heated area sometime before installation to allow them to warm up. Move the barrels near the PDU they'll be wired and open the lids to let the air circulate. To speed the process, pull the coiled power whips out of the barrel and set them next to the rack or cabinet they'll serve. Remove the tape used to coil the cables and allow them to warm; they'll begin to uncoil naturally. Once warm, slowly and gently uncoil the power cables being careful not to force the cables straight. Once uncoiled and warmed up, the cables will tend to straighten out and lay flat. Now the cables are ready to be installed.