Well to give you an estimated range of tomorrow's temp, which is kind of the best I can do with 0, is to say that it will probably be between the next closest temp which is 2 x -1 = -2 and of course 2 x 1 = 2.
The final guesstimated approximate range taken from closest above and below temperatures (in wholes) of 0 is thus
between, but not
-2 and
2.
Edit: But if you were to tell me, no please be more specific, then I would have to go with -1, why? because your asking
twice as cold, not twice as hot, therefore a lower temperature is logical, but since a temp of -1 today would result in -2 tomorrow, and the number here is 0 and not -1, I would say ok ok
-1 if you insist on precise number.