At first, the random thunderstorms confused everyone at Camp (they even scared some). But people were used to it now (or at least not as dumbfounded). The storms would occur every time Nico and Thalia fought (sometimes it was because Nico was hurt). It was understood.
But the day that the rain didn't let up everyone knew something was wrong (more than just wrong).
"Maybe they broke up," someone guessed. (No, that wasn't it.)
It wasn't until they found Thalia sobbing by her tree that they learned the truth.
Nico Di Angelo, King of Ghosts, was now a ghost himself.