Above ground pool liners are made from PVC which is a thermoplastic. This means the liner becomes more flexible when it is warmer and so it is important that when you are installing your above ground pool liner, you pick a day temperature that is warm enough to get the flexibility you need to fit the liner.
A good place to start is to ensure the day temperature for4cast is at least 15 degrees Celsius as below this temperature the liner will be too stiff to work with and if you strain the PVC, it cause cause it to tear. Liners being installed in low temperatures near zero have been known to crack when kicked into place use using a bare foot. The cracking is not a fault in the fabric, it just means the temperature is too low to install the liner.
Your should consider where the liner is being stored prior to installation as well. Even though the temperature forecast is above 15 degrees, the liner if it was left in a shad or garage or outside the previous night, could have a very low core temperature. Therefore it is recommended to store the liner in a heated environment on the night before it is to be installed. Any temperature above 15 degrees Celsius is suitable. This means the liner will be pliable and unfold from the box without the risk of cracking from the cold.
Some professional liner installers in very cold climates like parts of new Zealand have been know to use steam cleaners to warm the liner surface during installation. While this make work for them, it is not recommended by the manufacturers as there is still some risk the temperatures is not even through the liner and the PVC gets damaged.
So before you install a liner, check what the forecast temperature is going to be and make sure the liner is stored above 15 degrees Celsius the night before to reduce the risk of cracking or tearing during installation.