Howler

"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.

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.

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.

Behind the scenes

 * Instead of simply being a red envelope that can explode, in the film version of Harry Potter and the Chamber of Secrets, Ron's Howler resembles a mouth with teeth (simulated by the red envelope and white paper, with a ribbon for the tongue) that screams at the recipient, then blows a raspberry and tears itself to shreds once finished shouting. Also, Mrs. Weasley added a congratulation directly to Ginny for making into Gryffindor, stating that her parents are proud of this sorting. This implies that the film version's Howler possesses a certain degree of sentience and awareness of it's suroundings, as it turned to face Ginny to make this comment, changing its tone into a more calm and kind one.
 * In the film adaptation of Harry Potter and the Order of the Phoenix, Mafalda Hopkirk's letter floats characteristically and talks in an official tone to Harry Potter (the letter's sealing wax shapes the mouth). While there's no confirmation on this, this letter can be considered a different kind of Howler. Later in the same film, in a non-canonical Educational Decree, Dolores Umbridge referred to the Howlers as "Red Howlers", supporting the theory that there may be several kinds of Howlers.
 * For the Howler scene, Julie Walters had to scream so loud that she almost lost her voice at the end of the day.

Appearances

 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * LEGO Harry Potter: Years 1-4 
 * Harry Potter: A Pop-Up Book
 * The Wizarding World of Harry Potter
 * Harry Potter Trading Card Game