Why is the weather during the launch of Shenzhou IV cold not only physically, but also mentally?

In the first three launches, the problem was not the rocket, but the spacecraft. But this time the problem is neither on the rocket nor on the spaceship, but on the weather! For a time, low temperature has become a major focus of the entire launch field. It's really cold, especially for astronauts who are busy with rockets and spaceships. Not only the body is cold, but also the heart is cold, especially the leaders of the launch headquarters.