One morning in mid-December, Hogwarts woke to find itself covered in several feet of snow. The lake froze solid and the Weasley twins were punished for bewitching several snowballs so that they followed Quirrell around, bouncing off the back of his turban.

- Harry Potter and the Philosopher's Stone

“Very nice, dear,” said Neville’s grandmother in a falsely cheery voice, patting his mother on the shoulder. But Neville said quietly,
“Thanks Mum.” His mother tottered away, back up the ward, humming to herself.
Neville looked around at the others, his expression defiant, as though daring them to laugh, but Harry did not think he’d ever found anything less funny in his life.
“Well, we’d better get back,” sighed Mrs. Longbottom, drawing on long green gloves. “Very nice to have met you all. Neville, put that wrapper in the bin, she must have given you enough of them to paper your bedroom by now.…”
But as they left, Harry was sure he saw Neville slip the wrapper into his pocket.

- Harry Potter and the Goblet of Fire

Hermione had taken his hand again and was gripping it tightly. He could not look at her, but returned the pressure, now taking deep, sharp gulps of the night air, trying to steady himself, trying to regain control. He should have brought something to give them, and he had not thought of it, and every plant in the graveyard was leafless and frozen. But Hermione raised her wand, moved it in a circle through the air, and a wreath of Christmas roses blossomed before them. Harry caught it and laid it on his parents’ grave.

- Harry Potter and the Deathly Hallows