It's not that simple, ask any farmer: the amount of rain and when it falls, is hugely important too. The type of soil too, the new areas might have a wrong typ

It's not that simple, ask any farmer: the amount of rain and when it falls, is hugely important too. The type of soil too, the new areas might have a wrong type of soil for the grains. Even if the average temperature is the same, the amount of food you can produce can vary a lot.