I have a headcanon where Hex and Raven used to love watching the full moon together, but especially if it was lightly cloudy or foggy outside and the moon shone bright through the mist. They loved the full moon regardless of the conditions of the sky it found itself in, but something about seeing the light through the obscuring darkness captivated them in a deep way they, at the time, were too young to understand. But now Hex knows why. So every full moon that he's home, he checks the sky, and when it's overcast but he can still see the yellow sphere shining through, he rushes to his room with hot cocoa just the way Raven liked it and hunkers down in his favorite chair facing the window, spending time with his beloved sister.
(Coal never really got used to the spices of Mexican hot cocoa, but whenever he's there with Hex, he holds his own cup to the moon and drinks.)