- "You'd better open it, Ron. It'll be worse if you don't. My gran sent me one once, and I ignored it and — it was horrible."
- —Neville talking to Ron about his Howler[src]
A Howler is a magical letter in a red envelope which enchants the written message into the writer's voice, usually at a very high volume. The physical temperature of the Howler begins to rapidly increase upon delivery, and it will explode if left unopened for too long. This mechanism ensures that the recipient will open the Howler, even though he or she knows that it contains an unpleasantly loud message. Once the message has been received, the envelope bursts into flames, leaving only ashes.
The purpose of the Howler is to deliver a message expressing anger or great displeasure in a manner which standard writing cannot adequately convey. As such, a howler will convey the displeasure of its author/sender even if left unopened, for it will shower the recipient with insults and cursing upon exploding.
People who have been known to receive Howlers
- Neville Longbottom mentioned receiving at least one howler from his grandmother before 1992.
- In 1992, Ron Weasley received a Howler from his mother after he stole his father's Flying Ford Anglia.
- In 1994, Neville received a Howler from his grandmother, after he supposedly misplaced his password list enabling Sirius Black to enter Gryffindor Tower.
- A significant number of Howlers were sent to the Ministry of Magic in the summer of 1994 after the disturbing events of that year's Quidditch World Cup. The Howlers were primarily critical of the security precautions, and they caused appreciable damage to Percy Weasley's work area.
- Also, on that year, Hermione Granger received a few Howlers from readers of Witch Weekly when Rita Skeeter wrote a nasty article on her.
- Harry Potter's Aunt Petunia received a Howler in 1995 from Dumbledore when the Dursleys threatened to kick Harry out of their home after two Dementors attacked Harry and his cousin, Dudley.