At about 7:35, Avon states that the polar regions' temperature is close to absolute zero. Absolute zero is 0 degrees kelvin, or -237 degrees Celsius. This is a theoretical minimum tempreature where even the atoms in a molecule no longer move. Even the atmosphere would freeze.
Major Provine tells the Sergeant to wait 4 minutes until they are at the rocket bay and then start the countdown to destroy the planet. But if the countdown is over an hour, why wait and risk the control room being over-run, which it is.