what are specific examples that make the bitter cold seem real to the reader?

"He spat again. And again, in the air, before it could fall to the snow, the spittle crackled. He knew that at fifty below spittle crackled on the snow, but this spittle had crackled in the air. Undoubtedly it was colder than fifty below—how much colder he did not know."

Basically his spit froze before it hit the ground. It was also 70 below!

"But rub as he would, the instant he stopped his cheek-bones went numb, and the following instant the end of his nose went numb. He was sure to frost his cheeks..."

He also had to hit his hands on his legs to get any feeling.