Guess your army should stock up on Caravans and do some raids in another Realm 
I don't think you grasp the size of the problem.
There is a single weather zone that runs from the southern island (where Fissoa and Luria Nova are) all the way up to Libero Empire. It nearly completely contains multiple realms, and runs through at least 5.
Furthermore, there's no reasonable way that that much land should have the same weather at the same time. It should be broken up into at least 4 separate zones.
