I'm trying to reconcile two quotes from J.K. Rowling. She said that Dementors can't be destroyed:
You cannot destroy Dementors, though you can limit their numbers if you eradicate the conditions in which they multiply, ie, despair and degradation.
and that the weather became nicer now that the Dementors are gone:
Do the Muggles notice that there aren't any weird things going on now that Voldemort's gone?
Yes, the world seems a much sunnier place (literally - with the Dementors gone the weather gets better!)
How are the Dementors "gone" if they can't be destroyed? There was some conjecture that Dementors can die a 'natural' death (whatever that would mean for a Dementor) but it seems that the weather improved quite rapidly. Did the Ministry "contain" the Dementors somehow or did they die naturally fairly quickly?