It'll do it for temperature type variables, and also for cumulative rain versus E.T's. but not for humidities.
For example, if we look at the attached graph, we can see that although the loft temperature hasn't fallen below 0, it is being scaled to -10 because it is being plotted with the external temperature, which has dropped to just above -4. If the loft temperature was being plotted on it's own, or with something that isn't a temperature type, it would scale to 0 to 10.
I've added it to the todo list.
Cheers,
Stu.