Twice as cold is a meaningless question as theres no such thing as cold. Only an absence of heat. Your question would be better asked what would tomorrow’s temperature be if it is half as warm as 0 degrees.
Although this question has its own issues, as others have pointed out: to answer this question, one needs to know the scale. Since no scale is given, I feel that kelvins is the scale to be used as it is most typically used in science. In which case: 0/2=0
