“Raining . . . in your office? That’s—that’s not good, is it?”
-- Ron Weasley as Reg Cattermole (DH12)
Atmospheric Charms affect the weather inside Ministry of Magic headquarters in London.
When Hermione and Ron infiltrated the Ministry in disguise during the Voldemort regime, Ron’s alter-ego Reginald Cattermole was supposed to stop the rain that was falling in the office of Yaxley the Death Eater. Hermione whispers to him that if something has gone wrong with the Atmospheric Charm, then the incantation Finite Incantatem might not be enough to stop it, as it would with a charm or hex (DH12).
From the Web
"Atmospheric Charm" on Harry Potter Wiki